Team Fortress 2 - Did You Know...

[Antwan]

When the Heavy is killed while holding the Sandvich, it's dropped on the floor and anybody can pick it up for 50 health. However, the Scout gains 75 health instead, possibly a reference to a line where he says, "I. Eat. Your. Sandwiches! I eat 'em up!" This also happens with the Buffalo Steak Sandvich.
Video: http://www.youtube.com/watch?v=Dni6cPkD0iY#t=1m18s

Speaking of the Buffalo Steak Sandvich, as part of the Native-American themed Hibernating Bear pack, the steak was originally going to be a peyote cactus. It was removed because playtesters thought a man wearing a headdress and beating people up after eating said peyote could offend people.
Picture: http://farm5.static.flickr.com/4073/4735...aee6_b.jpg
Proof: http://wiki.teamfortress.com/wiki/Buffal...ich#Trivia

The Red Tape Recorder has three different sounds when it saps an Engineer's buildings. The sound that saps the sentry has somebody saying "Let's make some noise" that can be heard if the sound file is slowed down.
Sound: https://www.youtube.com/watch?v=NN3grbaJwE0

The Submachine Gun was originally intended for the Scout. The game file for the weapon is called tf_weapon_smg_scout and the first trailer of Team Fortress 2 has the Scout running with the SMG.

Also shown in the trailer, the Demoman was originally going to get The Dynamite Pack, a bunch of dynamite strapped together and thrown like a grenade. It was scrapped along with other potential grenade weapons.
Trailer: http://www.youtube.com/watch?v=9gv3XmD7-rk

TF2 originally had a Real Time Strategy element with a class known as the Commander. It would've originally oversaw the whole battlefield to lead groups as well as place buildings and start air-strikes. Commentary by Robin Walker reveals that the class was scrapped due to balancing and complexity issues.
Commentary: http://www.youtube.com/watch?v=lc6KGB81HQI#t=8m48s