This is a really tough question. Everything is my favorite for different reasons.
All my vintage stuff, because it's what started me on this little frenzy and are my favorite childhood toys.
All my original framed movie posters up in my living room (now that I have all six!)
My MR Obi-Wan sabers, just because they look nice on my desk.
Also I really like my "oddball stuff"--The SW Nascar cars I have, the film trailers, Darth Tater, C-1, C-3 and insider passes (Need to get the C-2 ones) and the Disney items Jedi Mickey, Darth Mickey and the star tours pass, just because they're not the standard action figure n such have a great appeal to me.