There really aren't many lenses you can put on the front of your SLR that you'd be 100 percent happy with if they were your only lens. But this EF 35mm f/1.4L might just be a good candidate with which to try. The bright f/1.4 maximum aperture makes this one of the most light-sensitive prime lenses in its class. When that aperture is wide open, it generates creamy-smooth out-of focus backgrounds that make your foreground subjects stand out against the screen or page.
The 35mm focal length is one you'll find useful again and again — as a moderate wide-angle lens on a full-frame camera, or more of a "normal" lens on an APS-C camera that will document the world in a very naturalistic fashion.
The build quality is everything you'd expect from a Canon L-Series lens. It has a satisfying heft and superb optical construction that will stand up to years of professional-level workload. Give it a week on your DSLR and see if you feel like replacing it all that often after you've seen what it can do.