Borderlands is one of the few Xbox 360 games that I managed to finish with 100% of the achievements. If you are unfamiliar with Borderlands, it is an over-the top frag-fest of epic proportions. The game is a little "cartoony" and your character is all about amassing bigger and badder firearms and learning to fighter bigger and badder enemies.
The weapons that drop as loot vary by type (pistols, rocket launchers, rifles, etc.), power level, and rarity. There was a way to duplicate the über-rare weapons with others and there were some hacks/cheats going on so some of the over-the top stuff was even more-so than it should have been.
Of course, some of the challenges were so ridiculous that you needed every bit of help. Mad Maxi's Underdome Riot had four arenas, each of which took several, about four, hours to finish. Working towards 100% achievement completion was a total pain in the ass......
...but this video trailer for Borderlands 2 makes me want to do it all over again: