...game? I want to buy my friends each a copy of a good, cheap (say under $20), multiplayer PC video game for Christmas. I don't necessarily care the genre (they're pretty flexible).One example I can think of (that they already own) is "Moonbase Commander".

I think you can give World of warcraft a try,
It cost more but worth getting it.

Try out Diablo games, they are a classic and still a lot of people play them. Its an RPG.

If you like action genre I highly recommend Call of Duty (the first one) I played it for about a year

Also, you can get counterstrike source pretty cheap. Im sure you can find it for 20 bucks or under. It usually comes in packages withother stuff. Which is a good deal because for like 20 or 30 bucks you get Counterstrike and other games like half life 2, day of defeat etc. Plus tons of people play counterstrike online.

You can some FPS for free - like America's Army. I haven't tried them but the price is right.

However, if you want a REAL classic, get M.U.L.E. via an emulator - there are some that support multiplayer online now! That is a fun game from the 80s!

Tim