Red Orchestra... the best multiplayer WW2 game out there, IMO, even though it only concentrates on the Eastern front. Very realistic. I just want a "British & Indian vs Japanese & Thai on the Burmese front" game now - it's pretty much the only WW2 front not covered.
Has a lot of potential, too, I reckon, combining WW2 with 'Nam.
Enemy Territory: Quake Wars demo... pretty good. Couple of balancing issues (ie. the Strogg can win 90% of the time if the team is half-competent) but the quality of the map is good. Hopefully the other maps included in the release will be of the same quality as the demo's map.