favorite commercial jig, the one I use all the time is the Rockler Table Saw Sled. After I set it up, it delivers such precise cuts I can't believe how close they are. Table saw sleds are often shop made, but the ability to cut any angle (to the blade) up to 50 degrees delivers so much versatility that it has become my most used jig.
Among shop made jigs, I like my fairly new miter sled, (pix 1) set up to cut right on 45 degree angles for picture frames. I fussed like crazy while making it to make sure the angle was just right. Going to make one change. I made a sliding stop block that locks in place, but made it with a 45 degree angle (pix 2). Should have done a 90, square to the jig's fence. I will be changing that to get a more positive stop position. The 45 degree angle allows slop.
I recently made the small parts cutting jig (with the circular base, pix 3 below), which is close to being a work of art to me at least. I haven't had much chance to use it yet other than test cuts, but I know it will be very helpful in future as I do a few more fancy projects.