I really enjoy the olympus lenses adapted to canon EOS. They have no issues with mirror clearance on the 5D line. The 35mm focal length is kind of a week one for the system though. If money's not an issue though, and you want something nice, I would buy something new and modern. I play with the olympus lenses because they are pretty good and relatively affordable. If I sold all of my olympus primes I might be able to afford an L prime. Nothing's nicer than the new 35mm primes, if you're willing to pay for it.
Canon 6D, Canon 5Dc, Rebel T2i, Canon EF-S 10-22, Sigma 35/1.4, Olympus OM Zuiko 21/3.5, 24/2.8, 28/2, 40/2, 50/1.4, 50/3.5 macro, 100/2.8, Canon EF 20/2.8, 35/2 IS, 40/2.8, 50/1.4, 85/1.8, 200/2.8L, Contax/Zeiss 28/2.8, 50/1.7, 85/1.4, 135/2.8, Soligor 135/2