Hi all!
I am a very big fan of the old arcade game Spy hunter, (not spyhunter 2, that sucked)
here is a link to get a 3d spyhunter like game. Freeware
http://www.adamdawes.com/
it uses the tokomak physics engine, and you can have joystick or steering wheel controls…
here is another retor game re-make called Trackballs…
http://trackballs.sourceforge.net/
it is a rip off of the 1984 classic arcade game Marble Madness.one of my favorite games EVER!!
it comes with a level editor, so you can make custom maps… you can even upload your best work, and they might incluse it in the next release…
I am doing a re-make of marble madness also, useing the reality factory engine. I will post a download link as soon as I have an alpha release…
here is some more information on marble madness…
http://www.classicgaming.com/rotw/marble.shtml
Battle for wesnoth:
http://www.wesnoth.org/
tile based game , online game play, lots of single player levels also…
this is an open source project.
Soldat is an AWESOME 2d shootem up game…
this is most fun for online gameplay…
but it also has single player maps, and Bots.
Soldat has no anti-cheat protection, so the game runs very fast online, It works well on even a dial up connection.
This game is extreamily violent, with very graphic details.
Michal even has a type of ragdoll effect, which I have never seen in a 2d game before.
Nostalgy 
Pilou
This looks like a neat project
http://www.flightgear.org/
I realy liked flight simulator from microsoft when I was a child… this one does not look too bad…
you can build your own custom content too… here is the editor:
http://fgsd.sourceforge.net/status.html