For Oblivion
Clutter King: 0G
Collect one of every clutter item (spoons, pots, plates)

HG131:
COD MW 2
77 GS - We're Ripoffs! - Get 5 Sticky 'Nade Kills in 1 game.(It's called We're Ripoffs because Halo 3 as an achievement for this and MW 2 has sticky nades).

Actually, InFamous has an achievement for 100 static bomb kills. It's called 'Oh, So You've Done This Before?'
The static bombs are almost exactly like plasma grenades.

"Deulerific Dickhead: Challange your friends to a duel 20 times in 2 minutes -10G" Borderlands

(Seriously this is what all my splitscreen matches in borderlands turn out to be)

COD4 - Get the tent up! - Get 10 headshots without moving.

Halo 3- No Skill For U (0G)
Congratulations, you got a mythic map pack achievement while playing GRIFBALL.

Halo 3- Consolation Prize (5G)
Attempt to get Vidmaster: Annual and lose at least one friend from it

A for Effort - 5G

Die 15 times in a row without getting a kill. (COD2-5)

Rainbow Six: Vegas 2
Doorcamper (Gold) - Reach Elite rank within a day of release
Empty Casings (Silver) - Fire 10,000 rounds
There Are Three Kinds Of A.C.E.S. (Gold) - Reach maximum level for all A.C.E.S.
Paper Cuts Scissors (Silver) - Finish the final scene firing nothing but a pistol
Status Quo (Bronze) - Play the game without changing the starting loadout

Star Wars: The Force Unleashed
Mirrorman (Bronze) - Finish the stormtooper module without moving
The Force Is With Me (Gold) - Upgrade all powers and stats to the maximum

Need For Speed Carbon
Corvette Pusher (Silver) - Overtake Darius on the first corner and win
Pimped Out (Bronze) - Fill the My Cars garage