I've been trying for quite some time to come up with a procedure for weaponless combat that goes beyond the bare bones rule given in LL (pg. 53) but still stays true to the "basic" spirit of Labyrinth Lord and doesn't overly complicate things. Here's what I've settled upon:
Pummeling
Normal melee attack, d2+STR modifier subdual damage.
Grappling
Grappling attacks may only be made against creatures of equal or smaller size (unless defender is prone) and both hands must be free. If defender has a weapon, he rolls to hit each attacker attempting to grapple. Any attackers that are hit are fended off. (No fending off attack is granted if the defender is surprised.) Remaining attackers and defender each roll XdY, where X=combat level (20-THAC0) and dY=hit die type (monsters with less than 1 HD roll d6).
I. If the attackers' roll is higher, then the defender is grappled (cannot move, +2 to be hit without DEX bonus to AC, -2 to hit). The grapple is maintained until: (a) the defender is released, (b) the defender makes a successful melee attack against each grappling opponent, or (c) the defendant makes a successful counter-grappling attack, using the opposed roll procedure.
II. If the defender's roll is higher, then the attackers are thrown off and the defender (if armed) is granted a free melee attack against one of the attackers.
III. If the rolls are tied, then the combatants are struggling and the procedure is repeated in the next round.
Overbearing
Overbearing attacks may be made against creatures of any size. If defender has a weapon, he rolls to hit each attacker attempting to overbear. Any attackers that are hit are fended off. Remaining attackers and defender each roll XdY, where X=combat level and dY=die type by size (sm=d4, md=d6, lg=d8).
I. If the attackers' roll is higher, then the defender is knocked prone and stunned (unable to act, +4 to be hit without DEX or shield bonus to AC) for one round, unless he makes a successful save vs. breath attacks, in which case the attackers are thrown off.
II. If the defender's roll is higher, then the attackers are thrown off and the defender (if armed) is granted a free melee attack against one of the attackers.
III.If the rolls are tied, then the combatants are struggling and the procedure is repeated in the next round.
I'm beginning a new campaign soon, so I'll report back on how this works out in practice.