BEWARE! Mozart is deceptively difficult. As Schnabel said, "Mozart is too easy for children and too difficult for adults!" So true... Some of the early Sonatas are not, well, so interesting(lightning strikes Arensky dead) FOR MOZART!! (Arensky is revived). Instead of listing the "good ones", I will list the ones that are not so interesting IMO. K.279, K.280. Well that was short! Three are perhaps overplayed, K.332 in F, K.333 in Bb and the infamous K.545. The Sonata K.331 of which Alla Turca is the last movement is really cool, but if you wish to avoid the Alla Turca I understand, it's played to death! Space and time constraints prohibit me from a blow by blow description of each Sonata, you should listen to them (de Larrocha has recorded them all and she's wonderful) or read through them and pick one you like. Also there's the Fantasies in d minor K. 397 and c minor K.475, Allegro in g minor K.312, Adagio in b minor K.540, Rondo in a minor K.511, Rondo in D Major K.? and lots of Theme and Variation pieces, including one on "Twinkle Little Star" that is VERY dificult, you wouldn't want to screw that up in front of anyone!
So there's lot's to pick from, obviously. BTW Jan.27th 2006 is Wolfie's 250th birthday, there are festivals and celebrations everywhere on Earth; do join the party, he's great, maybe the greatest! Let me know what you settle on for your short list of candidates.