Hello,
In case of games, I'd suggest Prey - game works perfectly under WINE, and have some very nice graphics. There is a demo available somewhere.
And I agree with someone who previously posted that you should try Flatout 2 (though NFS: Carbon and both Underground I & II work fine for me too). You can try Oblivion too (does have a demo, but requires a decent graphics card and lots of memory). All games have a demo version, so you don't have to own them.
If you want to show some apps, try Photoshop. This is the app that most Linux users miss. Photoshop is big, advanced app that works almost fine (with few glitches, unfortunately it works slower than on Windows because of lack of DIB engine).
Cheers