1. Yashica GSN for apeture priority mode and a great meter.
2. Konica Auto S2 (great viewfinder, sharp lens that gives "swirly bokeh".)
3. Minolta Hi-Matic E (never owned one but they've got a great reputation)
4. Canon Canonet QL17 (Not sure if you can find it for under $50... Unlike the above it's small)
5. Olympus XA (these are going higher than I remember but you may get lucky.)
6. Olympus RC (Man, I remember when these were cheap, cheap... couldn't give them away... Again, you may get lucky. Probably better off looking at local Goodwill or a Craig's list)
I'm thinking I'm liking the smaller rangefinders these days if I were ever to go the fixed lens RF route again -- the Canon or the RC.