Everyone says #16 or Amen Corner, but I believe that I have a better spot to set up your chair.
The yellow is the ropes.
This spot has a good view of the action in a few places. You get to see the guys hitting approach shots into #13 green. You get to see them chip and putt on #13, then the players walk right by you on their way to #14 tee, and you get to see them tee off up close and personal (which is unbelievably impressive).
The other thing this spot has going for it is SHADE. Some of the more popular spots on the course are totally exposed and depending on the weather that could make for a rough day. Also there's a concession stand and a scoreboard right there.