its really hard to beat the M42 lenses from Pentax...the 17mm F/4, 28mm F/2.8, 55mm F/1.8, and 135mm F/2.8 are all amazing..
Even better is the "old" Canon FD glass...BUT, you cant use them on an EOS body without either a)losing focus at infinity, or b) needing to use a TC to get infinity focus, which changes the F/L and F/R's..
If you own an APS mirror-less(ie Sony NEX, Samsung NX, etc) the FD glass is BRILLIANT to use!!!
I know, I have been having a TON of fun with my prime FD collection(28 F2.8 SC, 50 F1.4 SSC, 135 F2.8) on my Samsung, and love it so much I may even sell my 7D for a Sony NEX-7!! as I dont really need the 7D but for the video..and the Sony will be even better, AFAIK..)
Most of these lenses are all had at <$100 each! some even less than $50! but the ultra wides(17mm F/4) will cost you a couple hundred $...
but its a lot of fun. and MF is actualy VERY easy on the mirrorless setups. I never cared for it on my EOS bodies....but do enjoy it when just 'playing around', but would never bother when actually working.. 
Good luck!!