I don't think armbars and shoulder subs hurt very much. It might be because I'm pretty flexible, but I only tap for those because I know if I don't I will be injured, not because of the pain itself. Ankle submissions scare me, so I always tap way before it actually hurts, because I know by then it's too late. I don't have a lot of experience with having kneebars put on me, because most people know I have bad knees. Wrist locks hurt quite a bit, but luckily most of the people I grapple with don't use them. Except for my husband, who is a Daitoryu Aikijujitsu student, and wrist locks are their bread and butter.
Blood chokes don't hurt at all, I only tap when my toes start tingling. I don't like when my face is covered and I feel like I'm being suffocated, but that's more scary than painful, and it usually won't cause me to tap. However, windpipe chokes hurt like a SOB!
In the end, there is a tie for the sub I hate the most. I'm torn between any form of the spine-twisting, back-breaking variety; for example a body triangle when they bend me backward (especially if their cup is digging into my back), or calf-cutters; which is often how I pay my husband back for wrist-locking me. Yeah, he doesn't like them, either.
Prince Humperdinck: First things first, to the death.
Westley: No. To the pain.