Team Fortress 2 is the funniest game since Psychonauts.
Best moments so far:
Red team's trying to get into blue's last control point, but can't break through the three turrets and one demolitions man guarding the point. Finally, one red medic gets his uberbeam charged, makes a soldier invincible, and they charge the point. As soon as the soldier steps onto the point, the blue demoman detonates the six remote mines he planted right on it. The soldier is launched so far in the air the invincibility beam breaks, and he dies instantly.
Second best:
A scout just barely ends up being the last survivor of a huge gunfight. He runs back around a corner of the building where it went on, and calls for a medic. As soon as he puts his hand up to his mouth to yell, a train hits him.
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"Only things I approve of should exist." -some guy on the internet