The rise of the achievement during this generation of games is a fascinating thing. Their usage and potential for both good and evil towards games and the people who play them will be debated for a long time to come.
I have no desire to talk about them in that context today, though!
Achievements, especially how they're usually implemented on the Xbox 360, tend to be little more than a meta-game. They're something to keep track of in addition to the things you may naturally do while playing. I was highly amused when achievements themselves started going meta. Well known achievements began to be referenced by other achievements. Without further ado, here are my two favorite family lines of meta-achievements on Xbox Live:
Gears of War
US Release: November 7, 2006
Seriously... 10,000 kills in multiplayer
US Release: February 7, 2008
No, Seriously 10,001 ranked kills in multiplayer
Battlefield: Bad Company
US Release: June 23, 2008
Beans Bullets Bandages (Online) Get 10002 kills
Gears of War 2
US Release: November 7, 2008
Seriously 2.0 Kill 100,000 enemies (any mode)
US Release: October 8, 2006
Zombie Genocider TYPE: 1 Play REQ: Defeat at least 53,594 zombies.
Left 4 Dead
US Release: November 20, 2008
Zombie Genocidest Kill 53,595 infected.
Dead Rising 2
US Release: September 28, 2010
Z-Genocider 2: Genocide Harder Kill 53,596 zombies
Zombie Genocide Master Kill 72,000 zombies
Rock Band 3
US Release: October 26, 2010
HOPO-cidal Maniac Kill 53,596 Hammer-ons and Pull-offs
Were you to complete all of these achievements, you would net yourself a paltry 265 points! I hope it was worth it.