Mine is absouletly Gobble Gooble on GTA IV. 
 
That name maked me laugh my ass off.

A Series of Tubes

Sounds pretty similar to this thread.
 
Regardless, the best achievement name in all aspects is What is Love? or Beat Golden Poo Snake.

The "Kill 1,000 Children" achievement currently present in Fairytale Fights sounds pretty hardcore to me.

Borderlands has an achievement called "My Brother is an Italian Plumber" where you have to kill an enemy by stomping on their head.

DiRT 2.
 
There's an achievement in it called '2 Cups 1 Girl'. You have to win two cups with a female teammate. And I kid you not.

Hmm thanks for all the hardcore names guys.

Icy Dead People.
 
I thought was pretty cool.

Hardcore - Get 1000 kills in Team Fortress 2.
 
Hardcore for sure.

"Hardcore - Get 1000 kills in Team Fortress 2.  Hardcore for sure. "