I'll say the toughest thing I've tamed recently have been Raptors. They are lightning quick and do not slow down as they take damage. They hit pretty hard as well. Throw in the fact that they might spawn a half-dozen friends if you move around too fast (secondary spawn if you run I think) and it can get pretty nasty. The other thing is that they move so fast, on my screen at least, they'll jump from a few tiles away to right on top of me in a split second, which only only means that they can bite me, but also that I might hit them in self-defense and interrupt the taming opportunity. I don't use peace or honor for any taming, so knowing how to move is critical. It's two bad that a pair of them with pack instinct doesn't seem to be all that effective to me.
GD's are tough because it has to be done on foot (5 slots). The flip side is that they slow to a crawl if you beat them down first, and their breath weapon does little damage when their HP are low. I think one mistake a lot of people do is use protection spell at all times, which I think is actually more dangerous at times against spellcasters like GDs. If you're not in protection, you can cure/heal/invis a lot faster; just gotta know how to time them. If you tame in Destard, it's pretty easy to separate a GD to tame in peace.
Do you guys remember trying to tame nightmares in Terathan Keep back when the nightmare spawn area was filled with Ophidians? The nightmare would spawn on that plateau there, and there would be what seemed like hundreds of Ophidians around. Taming was no picnic anyways, because it was capped at 100, and attempts on a 95.1 minimum skill nightmare was a serious test (5% chance maybe?). Throw in lack of faster casting, fast cast recovery, severe mana limitations, etc. That will always stick out in my mind as the ultimate taming challenge, and why for so long (back in the day) nightmares were the elite ride.
