1. Malvolio2. Harold, in Orphans3. Ezra Rosen, in Dangerous Writing4. Reed, in The Complete History of America, Abridged5. Colonel Radzi, in In the Matter J. Robert Oppenheimer6. Caliban7. Jacques8. David Wheeler, in Made Crooked9. Mr. Klemper, in The Boys Next Door10. Henry IV
Notice that the favorites aren't always the biggest (Radzi was small, but it was my first successful 'characterization,' and the first time I truly made people laugh because of a strong character choice I made.) Also, 11-15 are a very close tie with 6-10, there's a hair's breadth between any of these. My clearest favorites are 1-3. And, 1 stands above all. Malvolio rocks.*
11. Orsino12. Will, in Beginnings13. The Mayor, in The Front Page14. Duke Senior15. Drey, in The Trestle at Pope Lick Creek
Also, I can't help noticing: there's a decent amount of comedy in here.
*Last night, Aaron Adair pointed out to me that Malvolio is a warm up/training role for Shylock, and, I would add, Richard III, especially as I played Malvolio, with a lot of direct address.