I'm playing F.E.A.R Combat recently, and addicted to it a lot. Usually play in some Australian server (Game Arena, Turbo) because the ping is quite low for me (I'm in Indonesia).

 I'm not a PC geek, so anybody knows any good games beside that? Free is better :).

 I don't mind to buy any good online games, as long as I don't have to pay it monthly (like WOW)

I would recommend games from the developers of Valve. Counter-Strike is a good game and you can opt for older versions of 1.6 (oldest), Condition Zero (new maps and models, but essentially the same thing), and Source (an updated Counter-Strike on the Half-Life 2 Source engine). Day of Defeat: Source was also an interesting game (there is the original Day of Defeat, but I've never really played it). Team Fortress Classic was very fun in it's day, but I would recommend Team Fortress 2 in it's place. 

Not only that, but Valve also makes good singleplayer games too with the Half-Life series. I would recommend getting The Orange Box if you wish to play Half-Life 2, Half-Life 2: Episode 1, Half-Life 2: Episode 2, Portal, and Team Fortress 2. These are all good games, but you can get the separately if you wish. Getting the new singleplayer games should also make you able to download user created mods where you can get some interesting user created content. 

Also, Turtle Rock Studios, who are working on Left 4 Dead, was recently aquired by Valve. Left 4 Dead is a zombie game where 4 players (AI or human) play in online co-op and try to make it through a scenario while the AI director looks at their progress and sends tons of undead uglies at them. Not only that, but there are also 5 (4 can be player controlled) boss zombies that can further hinder the players. This is another game to keep an eye on as more information comes out. 

Thanks IllegalPaladin.

I bought Orange Box already, but couldn't play HL2:Ep2, and Portal because my laptop is suck (nVidia 7300 Go). Even when I got free games from Valve because of my nVidia, the Lost Coast made my laptop crash. Lol. That counter strike suggestion is interesting, never played it before.

Yes, I played Team Fortress 2 in lower resolution. it's real fun but I wondering why I can't play it well. Even I can't aim well, maybe because the style is so different from F.E.A.R

Call of Duty 4 + Team Fortress 2 covers all PC online multiplayer FPS needs.

I know the CS fans will kill me for this, but CoD4 is a better realistic combat FPS than CS or CS:S are.   

Enemy Territory is good for a free game, but the only people left playing are the clanners who have bot-like perfect aim, so it gets frustrating to play (and I don't suck at PC fps's either).

Other than that, go with what Naznatips said above.

Enemy Territory? Never heard that.

*check Googles*

I played my friend's COD4, but single player only.

Thanks!

Yeah, it's a completely different experience on the PC.  Lag free servers + 50 man server cap + speed and accuracy of a mouse and keybaord = a great game made much better.

 Naz wtf are you talking about?

do u wanna fight? 

Naznatips, you mean COD4, right?

50 peope in 1 server is cool. I should have tried it.

I played 36 people max in FEAR, it's very hectic but fun. Don't you guys playing FEAR too? None of you mentioned it. It's totally free.

Never really got into FEAR. I think there's a fair amount of better games out there to be honest.

I'm really into TF2, as well as COD4.