Are you asking for reverb in general (instruments) or for vocals?
For vocals, I'll second the ole Sonitus verb. Along with Breverb, and the ReMatrix & IRs, you're covered pretty well sonically, and you don't have to spend a dime.
Another freebie verb released recently that's surprisingly good:
http://www.kvraudio.com/product/orilriver-by-denis-tihanov If you feel you must spend some money, the Valhalla verbs are well-worth their $50 (each) asking price:
Room for natural spaces or
Vintage Verb for that old school Lexicon vibe.