No I like the Halo3 online ones, like getting 15 kills in a row. That was a good challenge.
By the way, no achievements in Halo3 (or any other game) give you any extra equipment or anything that makes it easier to win. You get the achievement and some points, it doesn't change the gameplay. Have you actually got a 360, because you don't seem exactly sure what achievements do.
You just keep saying OCD, nerdy or anti-social, without really understanding whats going on.
They are just rewards for doing things, not little unlockables. You might get an achievement for unlocking something, but the achievement itself doesn't change anything about the gameplay or your character or anything else. Anti-social nerd, WoW player or anyone else.
In games less popular though, say XBLA games, you can't get the online achievements after a few weeks, because you can't get an online game. That could have been thought about a bit more.
Regardless, what would be nerdy about completing a game?