3 activations only.

OpenTyrian and the original (now freeware) Tyrian here

I imagine that most of these have already been posted in threads already, but here is a list of my favourite free games.

Cave Story (download Deluxe or the Japanese version and the English patch)
http://www.miraigamer.net/cavestory/downloads_1.php

Gravity Bone (Scroll down to find it)
http://www.blendogames.com/">http://www.blendogames.com/

Grotto King (Same developer and website as Gravity Bone)
http://www.blendogames.com/">http://www.blendogames.com/

Harmony
http://rabotik.nl/harmony.htm

Action Doom 2
http://www.gamershell.com/download_33252.shtml

Desktop Dungeons
http://www.qcfdesign.com/?cat=20

Bounce!
http://www.indiedb.com/games/bounce

Bloom
http://www.indiedb.com/games/bloom

Mirage
http://www.indiedb.com/games/mirage

Ayla
http://www.indiedb.com/games/ayla

Flight of the Amazon Queen is now available for free @ dotEmu

The Windows version of the first Wing Commander game is now free, available right here. :)

I am a big fan of old Capcom games, so I really want to share my kind of fun:

Devil May Cry modding Community:
http://s1.zetaboards.com/InfernalWorks/index/

Resident Evil modding Community:
http://z6.invisionfree.com/Resident_Evil_4_PC

Get the Hi-Res and Keypad-mod for Resident Evil 4 and this could be the GotYAY port.

Seriously, Capcom should've done the porting themself, not Ubisoft. On the other hand, there wouldn't be the possibility to mod it.

This thread should stay alive.