Heh, I have actually done this...I sold about 
half my collection when my car died, and I sold 
some more when we got our house.

If I had no choice, I think the break down would 
be something like this- "bare necessities" if you 
will.

Fushigi Yugi- 5 cels
reason- my favorite series
Utena - 2 - 5 (would depend HOW desperate I was. 
^_^)
reason - the movie is probably one of the best 
anime ever in my opinion, for art, story, music, 
on and on and on.... :)
Devil Hunter Yohko - 4
reason- I love Yohko, Ayako, Azusa... 
Evangelion - 1 
reason- IT'S EVANGELION for heaven's sake.  This 
is THE series that got me hooked on anime.  Love 
those girls in plugsuits.  ^_^