[Standard] [Red/Black Aggro] What do you think?

First off, don't forget to link to the deck you're referencing.  For any interested parties, I believe this is it:  http://deckbox.org/sets/292646.

That aside, I've been trying to figure out how to make Rakdos aggro work in the current meta and have quite a few thoughts, so please excuse my long-windedness, as hopefully some of this will help.

1) Drop the Cryptborn Horrors.  I know you had been thinking this already, but they're really just not likely to come in as anything sizable, and even then, they're vulnerable to even simple stuff like Unsummon which can reduce them to a much smaller size.

2) This is a matter of personal preference, but I normally don't see much sense in having more than 2x of any legendary creature in a deck unless you expect (or benefit from) them leaving the field.  Think about it, having 2x Rakdos in your hand would likely result in you just sitting on a dead card.  Sure, the first one could be killed and then you have a backup, but for the rest of the time, that's just a dead card.  Further, you really don't want to clog up the four-drop spot, which, conveniently can fit things like Desecration Demon or Olivia Voldaren without straying beyond your colors.  The Demon would also help ensure you hit morbid triggers quite a bit.

3) If you have a third Thundermaw, definitely put it in.

4) Burn is good, but I'd put the Pillar of Flames in the sideboard and possibly even 1-2 Searing Spears.  The most useful of the burn spells are the Brimstone Volleys because of their added damage from morbid triggers.  But perhaps more importantly, use the black spells that are more hard forms of removal, i.e., Murder, Tribute to Hunger, Ultimate Price, etc.

5) I'd make sure you have a guaranteed source of damage to your opponent so you don't end up missing playing Rakdos because they have a solid defense - a few options here, Tormented Soul or just Rogue's Passage.  Neither would disrupt you a ton as a 2x of, but potentially guaranteeing you can play Rakdos is important.

6) Slaughter Games and Rolling Temblor are HUGE pieces to fit into your sideboard.  Both offer ways to deal with threats that, on average, a B/R aggro build would struggle with.  More pointedly I'm referring to Geist of Saint Traft and Invisible Stalker for the Temblors and Sphinx's Revelation and Sigarda, Host of Herons for the Games.  Those four cards are essentially immune to what you're doing and, in many cases, will totally wreck your plans so having these options in the SB can go a long way.

7) If you're going to run Mark of Mutiny in the SB, you should probably toss in a sack engine in the SB as well.  It's no good to take their Tusk only to give it back even stronger.  If you can take it, then sack it, you get the damage AND get rid of the creature.

8) You need some sort of a draw engine to help once you get to top-deck mode.  Sign in Blood is a great option.  Alternately, with Rakdos helping out, Griselbrand becomes much more affordable to cast and offers an option to draw cards.

9) Flying defense is HUGE as Restoration Angel is a hair out of range for pretty much every burn spell out there.  Vampire Nighthawks are great for this as they offer both flying defense and lifelink, which conveniently can erase the cost of Sign in Blood or even help outpace your opponent.

10) I'd consider looking at creatures with higher colorless mana costs to really capitalize off Rakdos' ability.  I know the card's designer actually stated he was put together with EDH artifacts in mind, but there are some options available in standard.  Balefire Dragon is definitely a good option and one I doubt most would be expecting - although one that would likely need Lightning Maulers to make effective.

11) I don't have a good answer for you on this one, but you need to think about how you will alter your play style or cards you might want to add to deal with Supreme Verdict, as it's never any good to be laying into the opponent aggro style only to have a wipe happen and be left with an empty board and an empty hand.

12) This is the last one, I swear.  If you're going this route, you should definitely pre-order 4x Skullcracks from Gatecrash as the current issue for aggro builds is to get enough damage in before their tusks and revelations start hitting the field.

*Phew* that was a lot to go through... take or leave what you like and best luck with it.

A few quick points:

I had thought this too for a little while, but Stab Wound does the damage during their turn, not yours - so that's a no go for getting Rakdos out.

This depends.  Do you mean a Rakdos deck as in R/B aggro? Or do you mean Rakdos, Lord of Riots himself?  The former is already a pretty established deck that's making noise on the pro-tour - although you would need to drop a LOT more cash to pick up the 4x Falkenrath Aristocrats and whatnot to pull that build off (and I don't like using other peoples' builds anyway). 

The demon himself, well, the real issue is that any deck build around him would need to ensure he hits the field first and stays put long enough to make your stuff cheaper.  My first thought would be to take the deck to B/R/G (aka Jund) to then bring in some other options.  That offers the opportunity for more mana-fixing via Farseek and Ranger's Path some tutor effects to ensure Rakdos makes it into play via Jarad's Orders and some BIG creatures with high colorless mana costs via Giant Adaphage, Thragtusk, Worldspine Wurm and even Borborgymos Enraged.  Lastly, the green would help ensure that you can survive board wipes as Golgari Charm could slide into the sideboard - the catch is, the deck we're discussing now is by no means aggro, rather, some sort of a Jund mid-range.  It's worth a go though...