I just went through this, myself. I shoot vintage military rifles for fun and in CMP matches. I'm most familiar with the 1907 style sling for sling supported shooting. So, when I put together my most recent, modern, "precision" rifle, I wanted to put a sling on it that could be used in a similar fashion, but I wanted to break away from the traditional a bit, too, by getting something with a little more flexibility. I ended up going with the TAB Gear Elite and I love it. It has a lot of flexibility in how you can mount/use it and allows me to get slung up tight, VERY quickly. The construction and materials are top notch, as well (and I'll admit that it was hard to determine the quality of it by the photos/videos on the web, where it can appear to look like many other $35 slings. It wasn't until I had it in hand that I fully realized what a quality piece of gear it is).
There are others out there, too and I'm sure people will chime in with their favorites. I would also check out the TIS quick cuff and Mountain Shooter sling, which seem to be very popular. If I hadn't gone with the TAB, it would have been one of those two, for sure.
John