So one of my buddies loves to play just FFA games running 2-4 players, sometimes more.
But nothing fancy, he just runs very regular decks that aren't exceptionally OP or don't have a lot of cheese.

As such I am trying to come up with a new deck for this exact occasion, focusing on lulz and havoc.

So any suggestions would be appreciated!

Initial concept is to build it around "on each upkeep" cards, starting with Timesifter.

What else can I toss in?

For fun you can play an EDH deck as a 100-card highlander in a FFA game like that. You'll probably win wince nobody will touch you for the first handful of turns and then you'll start dropping bombs that they can't keep up with ;)

This is a possibility, currently I am undecided how I feel about EDH and the others are rather against it :P.

Personally, I think it's the most enjoyable format for casual games that there is. I think you'd like it but I understand the apprehension of your play group takes precedence.

Can I suggest Paradox Haze?

I wanted to build a multiplayer "kill everyone" deck for a while to show people that multiplayer =/= slow. Cards like Flame Rift, Exsanguinate, Comet Storm, Manabarbs, stuff like that. I was originally going to play it with 4 Sol Rings and stuff like that (as the people who play "casual" essentially play vintage) just for extra gas, but decided against it. Seemed like a cool way to show my playgroup that multiplayer games can still end quickly, and you can still play powerful, aggressive decks.

Well here is the start of the deck; http://deckbox.org/sets/161067

Does anyone know what the card is that prevents your cards from being the target of spells or abilities.
I thought it was a global shroud, but didn't count for the card itself.

Proxied the deck to test out how it runs.
And its pretty stupid.
When I get a Tombstone Stairwell and Timesifter in play, its just silly.

It needs some more tweaking before I build it for real.

I run Tombstone Stairwell in an EDH deck and often combo it with Altar of Dementia. Maybe run that?

So we played a multiplayer game, along with my buddy on http://deckbox.org/sets/161560.
The game was so STOOPID, it was win.

At one point, we had;
Knowledge Pool
Teferi's Puzzle Box
Timesifter
Awakening
Black Market

Wanted my tombstone so bad.