In the day before yesterday's comments, I mentioned that I use a Basic Lift (BL) based "weight" for attacks for parrying purposes.
I can't recall exactly where I picked it up, except that I got it from Sean "Dr. Kromm" Punch.
I found Kromm talking about it here:
. . . where he off-hand suggests BL/20 for strikes, BL/2 for slams instead of ST/10 and ST, respectively.
So this isn't remotely my idea, but I figured I'd explain my execution of this nice idea I stole.
What I've been doing is BL/20 for strikes, BL/10 for heavy full-body moves (and two-handed strikes). I haven't been using BL/2 for slams, though, I think mostly because I house ruled that you can't parry a slam. Well, you can, but all you do is get to inflict a potentially damaging attack but still get slammed. We got very tired very quickly of people with unbreakable sufficiently heavy weapons parrying full-sized humans without too much difficulty, so "no" was much easier. Dodge it or Block it.
BL/20: Punches, most kicks, elbows, grapples, headbutts, strikers, shield bashes (sorry, shields don't count as weapons of their own weight in my games, because of this), etc.
BL/10: Bites, stomps, body checks, tail swipes, heavy strikers, two-handed combination strikes ("Hits with both clubbing arms" kind of stuff, or multiple-arm grapples).
BL/2: Haven't used it yet, but it would be for slams if I did.
Weapons I've generally been using the weapon weight itself, although for some I'll juice it up a bit or give them an exception if there is some reason why that makes sense.
Note: In all cases, calculate BL by Striking ST for strikes, Lifting ST for grapples. For example: A monster with ST 30, Striking ST 5 for bites only, and Arm ST 3 uses ST 30 for kicks, 33 for punches, and 35 for bites. This is rarely an issue, and you should calculate this ahead of time anyway!
I don't limit Block by weight, although for really heavy strikes I'll pull out the shield damage rules. The 3e ones made shields fragile, 4e extremely tough, but hey, if a giant strikes you for 7d+5 cutting, I'll going to want to check for breakage on your wooden Medium Shield. Of course, that only happens if you make it just by the margin of the DB. Otherwise, you've presented the shield well enough to cause the attack to glance off harmlessly.* Otherwise I've generally been ignoring shield damage as something I don't feel like tracking these days.
In any case, I think this would work fine for anything, not just DF, where I'm currently using it. I'd port this to any GURPS game. Parrying big animals should be tough!
* I've had people question that before, but the example I use is either car windows vs. gunshots (if they're familiar with that from reality instead of fiction) or taking (not checking) a kick. In my MMA training I routinely get kicked full power in the leg. If you turn into the kick and give it an angled thigh to hit, you can take it without much (if any) damage. If you don't turn into it, or you turn a little too poorly, you suck up the impact. Checking a kick is a GURPS Martial Arts Jam, and man that sucks for the kicker if you do it correctly.