Make fire giants (possibly only in the Valkyrie quest, possibly others) spellcasters who can only cast a fireball spell. Or, to avoid a flavor issue with giants being not very smart to be good at spells, flavor it as something other than a spell (it could also be implemented as a new attack type).

The player can shove things, dealing no damage but pushing the monster back. The monster can resist and fail to be shoved; it will resist a lot if the terrain you’re trying to shove it onto is bad for it (like water). You can only shove if you have hands, and you cannot do it to small or tiny monsters. Possibly an AT_SHOV attack should also be introduced for monsters to shove the player.

Make zruties eat every sort of food off the ground, including tainted corpses but not cockatrice corpses. Make them MZ_GIGANTIC and block line-of-sight. Give them a bull-rush attack that runs you over like a boulder trap but with more damage.