For me, it's a combination of how well the hole is framed, and the green complex. I like a little angle off the tee, forcing you to really focus on a line. For example, I really love the new gold tee at Prairie Dunes #5 even though I have no business playing that tee. The new tee and that first fairway bunker on the left really frames the tee shot. To me, it is a much more pleasing and interesting tee shot than the white or blue tee.
Among tee complexes, I love the 1st green at Oakmont,along with #3 with the blind uphill shot. I also enjoy the 16th there, the par 3 with the opening on the left with the green rising to the right side of the green. I can't recall, I think it's the first par 3 at Riviera, #4, that I really loved when I played there a decade ago. And once you've played it, who can forget #14 at Pebble? It is the one hole I could play over and over again, one, because it is a great challenge, and two, because I have yet to par it after 5 rounds. Not even close, to be honest. #17 at Prairie Dunes is about as wild as anything I have played, because anything in the front right quadrant of the green, well, is down in the big bowl.