Ok, I think that going with lesser known pieces are NOT the way to go. Take something like the Arnold, (I am using Weber 2 and Premiere Rhapsody for my auditions.) and just play the crap out of it. They would rather hear a great performance of something well known (which obviously means that it is a staple of the clarinet repetiore) than something that they have never heard. A pretty standard list of good audition pieces would be as follows:
Concertos : Weber (1, 2, Concertino, Grand Duo Concertante), Mozart, Copeland, A Sphor, Also, depending on the level of the school, some lower level schools may accept the 3rd Stamitz Concerto (Intermediate at best, I sightread it pretty much perfectly...). I would stay away from things such as the Neilsen, which (Unless you are amazing) would only show that you don't really know your limits...
Sonatas : The list here is endless. Arnold Sonatina, Brahms, Saint Saens, Poulenc, Hindemith (A bit modern, but hauntingly beautiful). Any standard sonata would be fine in this spot.
Other accompanied Concert Pieces : Debussy, Premiere Rhapsody (A great piece due to it's great range in styles), Rossini, Introduction, Theme, and Variations (Difficult, but doable and impressive), Finzi, Five Bagatelles (Also on the easier side of things...), Babin, Hillindale Waltzes (See I,T + V), Luigi Bassi, Fantasy on themes from Rigoletto (If you can circular breathe, PLAY THIS!, If not, don't bother.), Weber, Variations, Messager, Solo de Concours.
Unaccompanied Pieces : I wouldn't suggest playing anything unaccompanied except for the Stravinsky 3 Unaccompanied Pieces. Perhaps the Osborne as well, but other than that, most unaccompanied pieces hold little place in the classical clarinet repetoire.
I hope this list helps. I would look at the majority of these and find what fits your range of ability best. As far as etudes go, just play from the Rose, 7 and 17 tend to be a nice contrasting set.