Canon's king of the 50's
Justin has reviewed the Canon EF 50 f/1.2L for your reading pleasure. He had a lot of experience with the EF 50 f/1.4 and f/1.8, but it turns out he may have enjoyed the 50L a little bit more.
I'm a fan of the 50 f/1.2L over the 50 f/1.4 if your budget allows it, the build quality, AF performance and optics are worth the price of admission. There is still some talk about the focus shifting of the lens, although those talks have abated a lot over the years. That's not an issue I've ever struggled with for my style of photography, and I think most people feel the same way.
Canon EF 50 f/1.2L $1299 (in cart) at B&H Photo