Marchesa, Queen of Chaos (EDH / Commander)

Use an unusual variety of cool effects to get your opponents to fight each other whilst you sit back and rub your hands gleefully and pull the strings (but probably don't try to pull strings and rub hands at the same time).

Use the "Curse of" and "Impetus" cards, and Bloodthirsty Blade, to encourage people to attack each other, whilst pillowforting to encourage people not to attack you. Usually, let the monarch go right away so that people will fight over it (but if they don't, try to get it and keep it).

Assault Suit is AWESOME. You don't have many things to put it on, but even an assassin is something. A cruel play is Besmirch + Assault Suit - steal something, it has to attack, and you can get it back later. Alternatively, Rakdos the Defiler... if you can also use a goad card on him this is pretty much a wincon.

Rite of the Raging Storm can be a bit of a dud late game but if you get it out early it's amazing. This is a good Enlightened Tutor target if enemies do not have much in terms of blockers. You can also put the Assault Suit on one of the elementals (which lets you keep it).

Duelist's Heritage is another noteworthy card as you can make deals with it and cause your opponents to do a lot of damage to each other (also a great combo with RotRS - double-striking trampling 5/1s are pretty scary). Tip: don't double commander damage if it would put someone within one (non-doubled) hit of losing, as it's better to wait and double the next hit instead if you still want to, since then you have the option of letting a potential minion survive. This card is also a nice combo with Marchesa because doublestriking deathtouchers can usually swing in with impunity.

This deck is more about causing chaos than winning, but usually aims to by not being the biggest threat until it goes to 1v1 then hitting with a Ruinous Ultimatum or swinging in with Rakdos. Duellist's Heritage can provide a pretty big boost even if you don't have a big board presence.