Some good titles, and I'll count unfinished since there aren't many known from this era outside of Disney.
Since I didn't make a few clear myself, here's a few Lost Felixes I suspect would be classics if found:
-The Love Punch (1921) Felix uses elixir to cheat a boxing fight in order to impress Kitty. Sounds very funny, and it does seem that Messmer developed Felix's character very quick and knew how to get good comedy out of him from even the very early ones (not that they exist, a few do, but I haven't seen them, I just suspect from what I've read)
- Felix Baffled by Banjos (1924) Felix annoyed by Banjos. This one was offered in 16mm, perhaps it'll show up someday?
-Zoo Logic (1926) Felix releases the zoo animals into the world, much to their confusion. A clever idea
-Sax Appeal (1927) Similar to Banjos, but with Saxophones. Again, a funny idea
-The Last Life (1928) Felix kills himself 8 times to get insurance money and retire with Kitty. Gruesome, but it has to be funny