I have an x51 and these are the ones I've been playing lately:
1) Mastersoft SuDoku (Once I start it's hard to stop)
2) Links from Hexacto (Excellent Golf Sim)
3) Patiences Gold Solitaire (For when my head starts to hurt from SuDoku)
4) RealDice.com Texas Hold'em (trial version, I'll prob buy it)