I'm still quite new to transcriptions, so there's so much to discover yet...
But at the moment I enjoy
* those that I get to know via Audition Room or Youtube, so keep posting

* all Bach-Busoni choral preludes, especially "Nun freut Euch lieber Christen gmein" (as I'm practicing, this is turning into a love-hate relationship), "Ich ruf zu Dir Herr Jesu Christ" and "Wachet auf ruft uns die Stimme".
* Bach-Hess "Jesu Joy of Man's Desiring"
* Wagner-Liszt Tannhauser, Schubert-Liszt Standchen
* Godowksy transcriptions... those on Schubert's "Wandering" and "The trout" are really funny. And the Chopin studies (haven't listened through all yet, my current favourite is #4, the second study on op.10/2). And the Saint Saens "Swan"....
* Cortot's transcription of Brahms' lullaby 49/4 (thal, it's now on my desk, thanks again for suggesting).
* Swan, lullaby, ...oh wait, before getting too kitschy, I better stop here.