Best bang "for the buck" has to be Nikkormat. Very inexpensive camera. Almost always found in working condition for little money. You can mount the less expensive pre-AI lenses and you have metering.
Preferably Nikkormat FT2 to use modern battery.
Check out this page to compare models:
http://www.mir.com.my/rb/photography/hardwares/classics/nikkormat/html/history.htm
Canon equivalent in terms of price and performance today is FTb. Uses common FD lenses.
Other cameras mentioned above by others are good, but won't be as inexpensive.