Trackmania Nations Forever on Steam.
Project 64
Sam & Max Season 1 Episode 4 (Abe Lincoln Must Die) has been free since it was released on steam
True Combat: Elite[/SIZE]
Think Counter Strike, with classes, for free. And it’s small enough to put on a flashdrive, and uses idTech 3 so it can run on school computers.
[COLOR=‘Red’]Pirates Vikings and Knights II (free if you have a source engine game)… which I would think everyone here does.
and
[COLOR=‘Magenta’]PLASMA PONG! (the official site is down right now though…)
and
[COLOR=‘Blue’]Portal. LOL.
but srly, there is a guy that made it so you can play every Streets Of Rage game, with any character.
it’s called [COLOR=‘DarkGreen’]SORR, and it’s epic.
Albion.
High Sea Trader.
OH ! hahah didn’t see it before, wasn’t logged in imageshack
Albion is free? Didn’t know that. Not that it matters, I still have the original CD with it.
That looks quite good for the CoD1 engine, I might give that a try some time. 
this[/SIZE]
It has a big learning curve and can be quite punishing to newbies especially if you’re playing with veterans (watch out for Faravid, Eggzor, etc…) but if you get used to the game it’s so much fun. Really, try it.
[COLOR=‘Navy’]Counterstrike 2D
[COLOR=‘Red’]Gang Garrison 2
[COLOR=‘Lime’]Armagetron Advanced
also The Game
LOL!!!
The best free game out there is League of Legends… Especially if u like DotA from Warcraft 3
create acc here if u wanna try: https://signup.leagueoflegends.com/en/signup/index?ref=4c8d6f3468431795545545
I’d rather not.
Also, don’t spam your referral link.
Its pretty fun, actually, but if you don’t have a friend to help you you may find the learning curve less than gentle. (Read: A brick wall)
Isn’t modified id3 (almost) the same as GLDSRC?