Definitely the putt on 18 for me. I've teed of plenty of time with the whole world watching and it doesn't bother me. The putt can be nerve racking knowing what is on the line. Even putting with a few dollars on the line, I've missed a few putts. My father used to talk in my backswing, play with change in his pocket, and numerous other tactics in order to get me rattled. Used to work when I was younger but I'm not so sure now.
coming down the stretch on 18, needing a particular score. if i duff a tee shot on 1, i have 70 or 80+ more opportunities to bounce back. but i only have ONE opportunity to get 'er dun on 18.
Teeing off first. I've always had nervousness on the first tee but after that shot it goes away. I would welcome the situation of the putt on the last hole.
I voted needing a two putt to win, last guy standing.
I say this because, on the first tee, there are no expectations. So what if you hit a crappy shot? Nobody will really care, other than you.
Last hole to win? You bet there will be more expectations, and more people will remember IF YOU SCREW UP!! And, there are no opportunities to fix the miss.
Since my lag putting is solid, I voted first tee. The only time I can remember feeling any real butterflies the last 25 years was on the first tee with a group of scratch golfers that I didn't know. I do remember being so nervous in college before matches that I would throw up anything I ate for breakfast.