Reeder (www.reederapp.com), having tried many and stopped reading any RSS feeds for a good while because I got too frustrated with them all. It's a front-end to Google Reader, which I really didn't enjoy using.

Main thing I'd like is the smarts to filter out stories which are essentially the same, but perhaps not exactly the same.

Oh, and if I bookmark/star something, then next time the same story comes up, highlight that I've already seen it, or even suppress it.