Working portable games (not crappy solitaire type ones)

Doom! 1 and 2
you need the WADS though, and i use jDoom cuz its shiney. I also downloaded the old model pack (10mb)
the program does a autoscan for the wads
u might want to search google for zdoom, because jdoom probably needs a high end comp (3d!)
http://doomsdayhq.com

Truck Dismount
RAGDOLL PHYSICS!!!!!
the dummy is in the truck and you can set up obstacles for him, like put jumps on, and make the truck go fast. get the highest score by hurting the guy a lot. they also have stair dismount where u push him down some stairs. its in 3d too, and it probably works on all systems since it worked on my laptop which had a 64mb of ram, some crap 4mb sis gfx card, and 500 mhz amd k6.
http://jet.ro/dismount/

GridWars
it is a clone of a xbox 360 arcade game called geometry wars. its graphics are pretty neat. its like some cyber asteriod game with power ups. ITS A MUST HAVE.
http://www.incitti.com/Blitz/

HaloZero
a side scroller halo. it has vehicles and everything as well as multiplayer support (although the server isnt working right now). pretty good time waster.
http://www.halozero.new.fr/

Counter-Strike 2D
i havent tried this one yet, but it is packaged in rar format, and im pretty sure it would work. its a remake of counter strike, but in birds eye view. quite fun, as you can play online aswell.
http://www.fpsbanana.com/?section=viewitem.forums.threads.main.42563&4 (main download)

skins for cs2d
http://www.fpsbanana.com/?section=viewitem.info.games.all.4

if you know any others please post!!