This is part of a multi-blog series on the basic and secondary attributes in GURPS. If you're new to the system, what are some things you'll want to think about? GURPS is point buy, so it's not up to the dice, but rather up to you and your point budget to decide. Today we'll cover HT and FP.
Also see posts on Gaming Ballistic, Ravens 'n' Pennies, and the GURPS 101 page.
How much HT do you need?
My usual answer has been "as much as you can afford."
But unlike ST, DX, and IQ, there is a level of diminishing returns on HT. While ST, DX, and IQ all give your some straight-up abilities and lots of rolls to do good things and avoid bad, HT is largely giving you some straight-up abilities and rolls to avoid bad stuff.
Not only that, but the penalties to those rolls are fairly restrained.
Rolling to avoid death is a really important roll, even in a game with fairly trivial consequences for death. But it's got its own inherent margin of error (Mortal Wounds), too. I covered a lot of this ground already, writing about Death Checks in GURPS 101: Dying is Hard to Do.
The steepest penalty to Unconsciousness rolls is -4 (at -4xHP or below - see p. B419).
The nastiest poisons in the game rarely get as bad as HT-5 or HT-6, although they can be worse on occasion. Generally, though, beyond that level you tend to see more "No resistance" type stuff, so your HT doesn't matter.
Lots of advantages add directly to some HT rolls (Resistant to Disease, Resistant to Poison, Resistant, Hard to Kill, Hard to Subdue, Magic Resistance) or all HT rolls (Fit, Very Fit), too, and are so inexpensive for what they do they're a better choice than pure HT for those narrower purposes.
On top of this, HT isn't expensive and it is a pretty solid deal. It's 10/level, for a +1 to a lot of important (even life-or-death) rolls, one FP (see below), and +0.25 Basic Speed.
Basically, when in doubt, take HT 12 for 20 points and move on. Get a 13 if you're really hard to kill. A 14 if you are basically unstoppable in a Rasputin-like way, and above that doesn't matter so much. In a game with supernatural threats, you might want a bit more - err on the side of 13 instead of 12, 14 for really hard to hill, 15 for the unstoppable sorts. You do end up playing chicken with death, though, since you tend to stay up right until you go to negative five times HP.
What about magic? A number of spells do get resisted by HT, but the Rule of 16 (discussed before under IQ) helps you here. Combined with advantages like Fit and/or Magic Resistance, HT-resist spells are not a crushing threat, so it's not that useful to try to "max out" HT just to deal with them. Still, a solid HT score is very helpful against supernaturally-based physical threats.
You get FP on a one-for-one basis with HT, plus extras are 3 a level. The usual cap is 30% more than your HT, although there are other ways to get more FP if you really need them, such as Energy Reserve (GURPS Powers, p. 119.)
Are you using Extra Effort in Combat (p. B357), or not? If you are, FP is important for everyone. You can't have enough, and everyone should think about possibly getting more either directly or by improving HT. If you can't, it's much less important.
Are you using supernatural or exotic martial arts abilities? If you are, you need FP even if other people don't need to worry about it.
FP are only 3 points each, which is a steal when you're in a long combat and using magic or supernatural powers. But in general, it's hard to run out of FP in a normal game, unless you're in a long series of long combats. It's rare in my own games for PCs without non-supernatural powers to invest in extra FP.