There have been a few tendered on here, but I'm not yet aware of such a scheme having been used yet. Here's what some others have suggested:
Ideas include, but aren't limited to (plz make suggestions):
Specific life point (I'm at exactly 100) or opponent life point (taking an opponent to exactly 17)
First creature with specific P/T
Second player to kill a creature
Attacking for a specific amount of damage
First player to spend 10 mana on a spell
First player to have something of his copied
First player with 6 basic lands in play
You get the point. Again, if you have ideas, feel free. If any of the ideas above particularly interest you, let me know.
That Guy wrote:
Ooooooo....I love thinking about stuff like this.
Richard Garfield often has prizes for accomplishing different "missions" in the game when he gunslings, and what I really liked about his was they did a good job of rewarding creativity without being overly complex. Some ideas along those lines, and picking up on a few of your broad themes, might be:
(In all cases, the first person to accomplish the mission would win the prize, and exact numbers could be fiddled with.)
Overkill: Dealt 41+ damage to a single opponent in one turn.
Just Enough: Dealt exactly lethal damage to an opponent.
Straight Flush: Simultaneously controlled five permanents of the same color with five consecutive converted mana costs (e.g., Rofellos / Eternal Witness / Ravenous Baloth / Ursapine / Silvos).
Good Samaritan: Made an opponent gain 10+ life.
Salsa Dancer: Played the fifth spell on the stack at one time.
Pardon the Interruption: Stopped a combo that otherwise would've gone infinite. (Possibly subjective)
Mana Maze: Controlled 12 different lands at once.
I considered running an EDH side event at a recent vintage event I ran, but decided in the end that I didn't really approve of the concept. We did play out a fairly excellent 2HG game of EDH while it was still ongoing though.
Had I run it, I was going to have a points system, something like:
Last player surviving: + 30 (with degen. combo, only +5)
Eliminated player (each): +20 (with degen combo, only +5, with general damage +50)
Cool play, minor/major: +5/+15 (discretionary - and evidently subjective)
Then some colour specific things like:
Black - killed 3 or more creatures in one turn without a mass removal spell +6; discarded 3+ cards from opponent's hands +6; dug up a creature -2
White - gained 10+ life in a turn +5; controlled 2+ creatures with protection during upkeep +2; played a wrath -2
Blue - played 2+ spells in the mainphase +2; drew 4+ cards in a turn +2; bounced 3+ permanents in a turn (not mass bounce) +5; countered a spell -2
Green - controlled creatures power 10+ during upkeep +3; played a creature with power 5 or greater +1; destroyed 3+ artifacts or enchantments in a turn +5; generated 12+ mana in a turn -2
Red - Dealt 10+ damage to at least 1 opponent in a turn +7; flipped a coin this turn +3; copied or redirected a spell +4; Destroyed a land -2
Haven't given it a whole lot of thought, but doesn't seem too gamebreaking.