Hi everyone, I've been lurking for a long time and I thought I'd finally get an account and join the conversation. I've been playing Goblins in Modern for almost two years now. I've tried every build, almost every card, and have piloted the deck in small, medium-sized, and large tournaments with success. Probably my best showing was at a ~250 person side event at GP Vegas. I placed top 8 and was one card away from winning the whole thing. Why the little preamble? Just to let you know I am a committed Goblins player, not just someone stopping by to see if they can't give Goblins a try.

Buckle up, this post is gonna read like a mini-primer (in-fact, I'd be happy to expand it and re-do the current primer if asked).

False Impressions and Common Mistakes

Many players approach Goblins from a budget or casual perspective, ignoring card choices or color splashes that help the deck perform immensely better in a competitive environment. While it is good that the deck is fun (who wants to play a boring deck?), and cheaper than most decks (not everyone can throw down $1,500 dollars), this means that there are very few highly skilled Goblins players are playing it competitively and contributing to playtesting, improvements, and making changes as the meta shifts. These factors contribute to the (false) impression that Goblins is not competitive enough for tournament play. I'd like to help change that. if I can.

Legacy Familiarity
Players familiar with the Legacy version of the deck attempt to port it to Modern without considering the differences in the formats. For example, blue-based, creature-light decks are very common in Legacy. Legacy Goblin decks prey upon this fact. Furthermore, there are some very powerful Goblin cards available only to Legacy players that practically require the decks to be built differently.
For example, Legacy Goblin players have Goblin Lackey, Goblin Warchief, alongside Goblin Piledriver and Warren Instigator at their disposal. This allows for powerful 4-5 mana cost Goblins such as Siege-Gang Commander, Krenko, Mob Boss, and Lightning Crafter to be much more playable. Furthermore, Legacy Goblin players do not have to worry as much about losing any particular Goblin from play, as Goblin Matron and Goblin Ringleader provide powerful ways for the deck to restock their hands with more Goblin goodness. The availability of Gempalm Incinerator and Pyroblast further contribute to the two decks being quite different.
These differences all combine to mean that Legacy Goblins is much more willing and able to play a more midrange style game featuring Aether Vial. If only Wizards of the Coast would reprint or reprise some of these cards, perhaps Modern players could have more freedom to build decks in a similar manner.
In summary, attempts to port the Legacy deck over have generally been unsuccessful. I'd love to be proven wrong, but I've tried it myself, with only moderate success.

The Many Faces of Goblins

We all know that Goblins is a highly customizable deck that can be played in a variety of similar, yet distinct ways. While this makes deckbuilding, playtesting (and primer writing) a more difficult task, it allows Goblins players flexibility in their card choices and the ability to tune it to a variety of metas and playstyles. Aside from the aforementioned Legacy-port style decks, there are basically two different styles of Goblin decks that I've seen put up real results (and by "real" I mean beyond reports from small events at local stores). I should also note that I've seen hybrids and slight variants of these decks also perform well.

1. Token-Oriented Goblins – Token Goblins relies on some combination of Mogg-War Marshall, Dragon Fodder, and Krenko’s Command to pump out as many goblins as possible. Foundry Street Denizen is a bit of star here, as he is able to get pumped to 3/1 very consistently. After playing these cards, Token Goblins blasts in with cards that pump the whole team, such as Goblin Bushwhacker, Goblin Chieftain, and Shared Animosity. It features a go-wide strategy that emphasizes the card advantage these cards bring to the table. It does well at fighting decks that rely on targeted removal. Obviously weak to sweeper effects such as Pyroclasm and Anger of the Gods, Token Goblins can also reestablish a board presence a little easier than some versions of goblins (albeit with creatures without haste and low threat density).

2. No-Lords Goblins - This is probably the most successful version of the deck. It focuses on speed and plays hasty, high-powered creatures and then finishing the job with burn spells (especially Goblin Grenade) to the face. While it may run many of the same cards that a Token Goblins list would (like Goblin Bushwhacker), it will probably run them in fewer numbers and/or be less reliant on them to win. The remainder of my post will focus on this build, since its the one I've found the most success with and I feel is best.

On Piledriver

While I love Goblin Piledriver, playing him requires you to build your deck around him. He becomes kind of a pseudo-lord, and a deck built around him feels a lot like the goblins lists I used to run that had lords. When he dies, the game plan often falls apart. I don't recommend playing him, except maybe in the sideboard if you expect Merfolk.

My No Lords List - Goblin Deck Wins

There have been a lot of discussion about which Goblins to run, but I have found that the more I run non-goblin cards, the better the deck gets. You might be surprised by some of the choices here, but give it a try and see what happens. You might think it isn't enough goblins to justify the x4 goblin grenade, but it's not. I'll post the list, explain the choices, and would love to get some feedback and fellow playtesters on MTGO going to further optimize it.

Goblin Deck Wins

1 Drop Creatures
x4 Foundry Street Denizen
x4 Goblin Guide
x4 Legion Loyalist
x4 Vexing Devil
x2 Monastery Swiftspear

2 Drop Creatures
x4 Goblin Bushwhacker
x1 Mogg War Marshal
x3 Eidolon of the Great Revel

Instants/Sorceries
x2 Mutagenic Growth
x4 Lightning Bolt
x4 Goblin Grenade
x4 Atarka's Command
x2 Searing Blaze

Lands
x4 Wooded Foothills
x4 Bloodstained Mire
x3 Arid Mesa
x2 Stomping Ground
x1 Sacred Foundry
x4 Mountain

Sideboard
x4 Destructive Revelry
x3 Pyrite Spellbomb
x3 Deflecting Palm
x3 Boros Charm
x1 Smash to Smithereens
x1 Rending Volley

Explanation -
x4 Foundry Street Denizen is included because he triggers off of every creature in the deck, he doesn't care if they aren't goblins, or if its a vexing devil going straight to the graveyard he's getting PUMPED!
x4 Goblin Guide - You hate to give your opponents cards, but knowing that a bolt is coming at your favorite creature is good to know. Oh, and he's the most aggressive creature in Modern and after he's been a traitor and given your opponents cards, blow him up.
x4 Legion Loyalist - Absolute all star. There are so many times where your opponents can't/won't block due to the first striking tramping team there's no way you don't run 4 of this guy.
x4 Vexing Devil - Sometimes a one mana boros charm that pumps the denizen. Sometimes a 4/3 that your opponent waits to bolt until he attacks (and then you mutagenic growth - absolute blowout). Sometimes a turn 2 big 4/3 trampler when legion loyalist gets his batallion on. Sometimes a t3 play w/ Bushwhacker that becomes 5/3 with haste. And yes, sometimes a topdeck that you wish was something else. He's worth it.
x2 Monastery Swiftspear - The weakest card in the deck, but probably performs well enough compared to mogg fanatic or any other one-drop. It dodges bolt with mutagenic, comes in with haste, triggers foundry street, and really likes atarka's command, searing blaze, and every single card in the entire sideboard. I consider this card a flex-spot, but I tend to keep coming back to it when I test with something else.

x4 Bushwhacker - One of the best cards in the deck and really pulls the non-goblins and goblins together into a truly synergistic deck. I liked playing x3 Bushwhacker, but he's just too good and it's important to keep the goblin count up high enough for goblin grenade, so its x4 for now.
x3 Eidolon of the Great Revel - You might be thinking, there is no way this card is good enough for goblins - and I resisted it - but I gave it a try and will never turn back. Think about this... our deck is SO fast, that we are almost always ahead in life total. If you stick this card t3 card with a goblin grenade in hand, you might not have won t3, but t4 is almost a certainty. The card single-handedly destroys storm and hurts many, many other decks. It gives us game against control (very, very important) and other decks that dump lots of cards on the table. It triggers foundry street and draws removal like a lighting rod. It practically guarantees at least some damage, not something you can say for too many other creatures.
x1 Mogg War Marshal - A flex spot for the deck, MWM is a card that makes it in due to comboing so well with foundry street and bushwhacker. It's a great goblin grenade target. Lastly, it helps put some goblins on the table to prevent not having a goblin grenade target.

x2 Mutagenic - Might seem very odd, but seeing how a well placed lightning bolt sometimes is the difference between a victory or a loss, something that counters it at 0 mana is pretty huge. It saves Guide, Devil, Swiftspear, and Eidolon from a bolt. With an atarkas command, it saves all the creatures from a bolt. Play with it, you'll find its a lot better than you might think.
x4 Bolt - Shouldn't need to describe why this card is included...
x4 Goblin Grenade - The whole reason to play this deck over burn or zoo.
x4 Atarka's Command - You MUST play this card. Never consider going below 3 - ever. Being able to maindeck lifegain hate gives this deck game against a wide variety of decks and prevents you from having to sideboard liefgain hate if you don't want to. Did I mention we go very wide and play TONS of one drops? This card makes the whole deck work. It also makes vexing devil not die to bolt.
x2 Searing Blaze - Probably the only card I consider truly, 100% flex spot. Against zoo, burn, affinity, infect, and more, this card pulls some serious weight. It clears the way for your Guide. Swiftspear (triggers it too), Vexing Devil and more.

Manabase comments - Being R/G for game one allows us to often fetch basics instead of shocklands. This saves life for the matchups against aggro decks (we're playing Eidolon, too, remember?). For matchups where our life total truly doesnt matter, we have the sacred foundry to give us access to some white cards that will help us in otherwise tough matchups.

Sideboard
Pyrite Spellbomb - saves us from straight up losing to Kor Firewalker. You can safely board it in, even if you don't know they will play it, because the card isn't bad on its own. It also kills etched champion and a few other protection targets that give us fits.
Deflecting Palm - gives us game against amulet bloom, bogles, tron (think wurmcoil engine) and any deck that plays big creatures. Good against burn, but I don't like splashing for the third color in that matchup. Basically the reason to splash white.
Boros Charm - a flex spot in the sideboard, B Charm is good for those matchups where you just want to become more a burn-like deck (control and some midrange decks).
Destructive Revelry - Gotta fight affinity and decks that rely on enchantments (twin, bogles) and artifacts with something, right? D Rev is the all star!
Smash to Smithereens - Smash that amulet of vigor and other pesky artifacts with this beauty.
Rending Volley - No twin, you will not beat us on turn 4, thats OUR job.