One of the iPod apps I've been most looking forward to lately is Reiner Knizia's Samurai, which was just released a few days ago.  I picked it up as soon as I could, and have gotten in 4 or 5 games so far.

Put simply, the app is absolutely incredible!  Unlike a lot of other apps, which tend to crash upon startup on my 1st gen iPod touch (I'm looking at you Medici and High Society), Samurai has been almost bug-free.  It's got a very nice interface and is playable solo against 1-3 AI opponents or in "hot hand" pass-around mode with other humans.  The style looks great, and there's some nice tutorial functionality with continuing quiz questions just to help clarify how scoring works.  When you finish a game, it will even explain to you why you won or lost if you want it to!

Plus, the game looks really great, plays quickly, and is a lot of fun.  If you're a fan of the boardgame (and have an iPod/iPad, of course), this really should be a no-brainer to pick up!