In my life and experience as a submissive, I can honestly say that I am not a pain slut, and my pain tolerance isn't quite where I wish it was. But that does not mean that I don't occasionally enjoy (or rather, sometimes deserve, depending on your point of view...) the occasional hard discipline.
I've been on the receiving end of all but one of these instruments, some of which were slightly painful but deliciously fun, others which were more painful but yet, if I deserve such discipline, then I obviously REALLY pissed her off- and it's a badge of honor to be able to take it, and hopefully, catharctic and satisfying for her to administrate it. I'll rate these in order of, well, impact:
1:: Basic flogger, or cat o-nine tails: Deliciously disempowering, harsh yet playful. I love being on the receiving end of this one. Although if she's in the right mood, she can totally unload on you with this one and it WILL hurt.
2: Leather paddle. Again, this shows her who is boss (and it sure as heck ain't me!) and I can definitely feel her wrath when she unleashes it. It can be a harsh, sharp sting, a deep bruising impact, or a playful spanking. Whichever it is, is not up to me.
3: Leather crop. These things sting- and hurt just enough to let me know- hey, you better stand there and take it like a b**ch. Just what a sub needs for light punishment.
4: Fiberglass crop. These things REALLY sting- and it hurts. You'd be surprised how much these little rods can hurt when she wants you to hurt. This is the point where it crosses the line from playful BDSM to more serious punishment.
5: The Wooden Paddle. For when a sub REALLY screws up. This is about my maximum limit. The one time I've had to use a safe word, was when I got hit with this a few times, and it brought me to whimpering like a baby. (Did I deserve it? You'll have to ask her!) I was proud, though, to have stood there like a man, for her sake, but this is where things get serious, as in serious pain. This is not playful light bondage anymore.
6) Bull Whip. She never went that far, luckily, as these things can do some serious damage, leave serious marks, and you'd have to be a serious pain slut for this- and it would take some experience and skill on the part of the wielder not to do serious damage. By my own admission, I'm not there yet, but if I ever screw up bad enough for her to try... well, that's really up to her, not up to me (isn't that the point of all this anyway?)
I've also seen even more severe instruments of torture- studded paddles, paddles with needles, some serious stuff that is literal torture. That stuff is for the real extreme players out there. At this point I'll say, stay safe, play safe, respect limits- especially your own.
Anyway, that's all I got for now.