PS--I do still play Battle for Wesnoth, 0AD, Warzone 2100.

Myth 2 Soulblighter back in 2001 under Mandrake Linux back then.
A great port from Loki of a wonderful RTS which still has an active community and is updated regularly.

What's the first game you played on Linux?

The first game I played on Linux was Xpilot back in 1994. It was also the first internet multiplayer game I played.


What's the first game you purchased for Linux?

That might have been Quake.


What's the last game you purchased for Linux?

The most recent games I've purchased would be the latest Humble PC and Android Bundle.
Before that, I picked up Wargame: Airland Battle in a Steam sale.


What free Linux game are you still playing?

Balanced Annihilatio (Spring engine), 0 A.D. and Angband

What's the first game you played on Linux?
I think it was tux racer.

What's the first game you purchased for Linux?
Never winter nights in 2002.

What's the last game you purchased for Linux?
Witcher 2.

Whats the next game you will purchase for Linux?
Most likely Wasteland 2 at some point.

What free Linux game are you still playing? 
Freeciv sometimes with friends. I don't really play that much of free games.