TPWitchcraft

I'm the captain of all who enjoy underground video games:

http://barbarian.1987.free.fr/indexEN.htm

Have fun :D

In no particular order:

Online/LAN:

Xonotic: Good for online/LAN-play. UT-Style FPS.

OpenRA: Damn well good. RTS.

Warsow: Similar to Xonotic, but much faster. Damn good game. Sadly, defunct.

Sonic Robo Blast 2 Kart: If you like kart games and think they are all to easy, this is your choice.

Online/Split Screen/Couch coop:

SuperTuxKart: Damn fun, especially with a few add on tracks and good company at your place.

Hedgewars: Similar to Worms: Armageddon.

Battle for Wesnoth: Really fun once in a while. Neither the online nor the local experience is really "better".

Offline/Split Screen/Couch Coop:

Atomic Tanks: Worms on steroids.

Barbarian: Rocks. The OSS-Version is a tad bit obscure.

I didn't do VCMI, but Homm3 is one of my big local multiplayer favorites. I wait for the full inclusion of WoG before shooting it up. Also, as a young boi I really loved C-Dogs. The thing is now open source, check it out.

Opposed to most other people here I would like to say that making your game support dependent from a software that 95% won't be able to install or use without getting a partly closed source DRM "app-store" software is - in my book - a bad idea.

Won't buy any games that have no native support.