To answer the emails: Canon EF 50mm 1.4 USM
It's sits on my camera 90% of the time and I'm reluctant to take it off unless absolutely necessary to get the shot. It's not fancy (by today's standards), cost much less than just about everything else excepting the nifty-fifty (50mm 1.8 MKII), and the AF motor is frail. That said, I've broken it just once, almost 4 years ago. Fixed it myself and it's been just fine ever since. At $300 and change most pros can afford to replace it once or twice.
I use it for fashion, commercial & lifestyle shots, occasionally swapping it off the 5D when I'm shooting beauty work. Landscape shooting is another application but most people prefer something wider to add some dynamic qualities to the picture..usually between 18 & 24mm.
It's a great lens because the resolution matches well with the 5D and 1Ds series cameras. It's actually pretty good on crop bodies too but then it becomes a telephoto lens with the 1X6 multiplying factor. It's also the sharpest 50 Canon makes besting even the 50L at anything from F/2.8 to F/22. I rarely shoot wider than that for my work anyway. The IQ is also not too far off from the L version, certainly nothing a little attention to post processing can't equalize.
I'll probably get hate mail from the 50L and Sigma fans...and that's cool. They are pretty much a cult anyway and we only need to keep an eye on them in case they start offering human sacrifices. I trust my eyes to tell me where my money should be spent.