A number of easter eggs have turned up in the PAK file for Quake 2. As
reported previously, there are the CFGs of the players and beta testers.
Also, it turns out that there are hidden, unused models for the nuke, mine, flare
gun, and disintegrator (all of these weapons were dropped from the final
game). There appears to be no way to play with them. Thanks Kami0. Also, it
seems as though 2 unused sound files are in the sound directory of the PAK
file, one named xianbeats.wav. I'll let you find those and listen to them
yourself :). Thanks Q11.

I just found a kickass secret at the end of Quake2...  it is better than
romero's head If you don't want to hear about it DO NOT read any farther...  otherwise
scroll down...

OK  I guess you want to hear...  After you beat the main stroggos guy...
go down into the rearming place in the basement of the final room....
at the end of the long hallway th wall is shootable...
this opens a passage to the "id gallery" where there are pictures of
almost everyone...  Some of the pictures also do stuff... Xian's plays
music... Tokays blows up.... Carmacks goes into the floor... Steed's
damages you....after you press all the buttons to see what they do... another hole
opens up in the floor.... revealing the "Tank Pimp" and a few of his
bitches.