Mine would have to be Roadkill for the PS2, think GTA meets Twisted Metal meets Mad Max and what you have is one shit storm of a fun game. Ive only ever found it twice, 1 for PS2 (which i bought) and 1 for Xbox. GTA is renowned for its witty humor, especially on its music stations, but Roadkill easily surpasses it, this one line makes it.
Random Caller to Radio Station - "Hey you guys, you ever done it with a pigeon, i have, then i had some pancakes, then BAM! Whacked my nuts on those pancakes, people dont want no Sexed up Pancakes."
Random ass Comments like that made this game so special.
Not to mention some awesome cheesy 80s power Metal, to encapsulate how awesome the music is, Dont Fear the Reaper by The Blue Oyster Cult is the theme song to this awesome game, More Cowbell!!!
http://en.wikipedia.org/wiki/RoadKill