Well I saw your response in the GTA:SA thread so I will not suggest that...

Band of Brothers is pretty good. As good a WW2 shooter as any other with the bonus of commandinf other soldiers. Not particularly detailed but fast, frantic and fun... Plus the added empahsis that everything you do is somewhat based on what happened to the real deal airborne troops during the D-Day landings...

HL2 is a blast too...

Have you tried the Battlefield 2 demo? It is fun, but I really liked Battlefield Vietnam so it follows that I would like BF2...

Nexus: The Jupiter Incident is a fun space blast, very pretty somewaht challenging, very good in the begining but gets a bit silly towards the end. Perspective and controls are not unlike Homeworld.

I bought Stronghold 2 a couple of weeks ago, it is a lot of fun but is full of bugs. I would wait for the 1.3 patch before picking it up if I was you...

The lastest version of Pirates is a lot of fun too. Gfx remind me of a more strategic version of Monkey Island. A great way to while away a few hours. Can get repetitive after a time though...