Dead Rising wins simply for the sheer number of odd achievements that give you something to do...Raining Zombies, Frank The Pimp, the novelty mask one...
Two from Mirror's Edge were interesting..."Hey, It's-a me!" where you do the stomp attack, and the one where you trigger the flip-off gesture. Some of the move-combo ones were interesting too, like "...aaaand safe!" where you have to combo together a wallrun, coil-jump over an obstacle, and a skill roll, or possibly "May I have this dance?" which is essentially a double wallkick.
CoD 5 had an interesting 5-pointer which you get after dying multiple times at the same checkpoint during campaign, called the Purple Heart. Easiest to get during Veteran, lol. Some of the multiplayer challenges are cool and/or funny, like "What The ?" where you kill someone by shooting a land mine through a wall, "You Talkin' To Me?" where you survive a tank round on foot and quickly destroy the tank, or "Oh No You Don't" when you destroy a mine immediately after it's planted and kill the planter in the process. And then there's always "Cruelty" where you kill someone, pick up his weapon, and kill him again with his own weapon.