In our house, only low-fat, preferably sugar-free ice cream is allowed. Not my edict, but my wife's. With that in mind, none other than Blue Bunny No Sugar Added (which I've only found at Wal-Mart locally) is the best I've run across. If someone handed it to me blind, I wouldn't be able to tell that it isn't full-fat and crammed with sugar. Really -- it has none of the too-airy texture that often betrays otherwise good light ice creams.
Favorite flavors are Chocolate Chip Cookie Dough, Turtle Sundae, Bunny Tracks, Peanut Butter Chocolate, Butter Pecan, and Chocolate Cookie Crunch. All very good.
As an infrequent (unfortunately) treat, Coldstone Creamery's Cookie Doughn't You Want Some, Oreo Madness, and Cheesecake Fantasy are favorites.