[aeberbach]

Did you look at Nethack? Certain monsters have set loot. Dwarves have a high chance of carrying a pickaxe, noble variants have a high chance of having dwarven mithril, shield, iron shoes. Same with Elves. Soldiers carry K- and C-rations. Paper golems leave piles of blank scrolls!

Monsters will pick up items. If you are in the dwarves mines and there's a mining dwarf about, gnomes and other creatures will pick up the piles of rocks they leave behind.

Additionally monsters with the right flag set will often use items. This can reveal their blessed/uncursed/cursed status ("The dagger welds itself to the goblin's hand!") or identify the item - which is sometimes a real pain, when a consumable you needed is used. ("The gnome zaps a wand of lightning! You die...")

[r00fus]

^ This.

Nethack is still unparalleled in how dangerous a monster can be with "your" loot (think you kill a monster with a magic missile, it drops loot, but before you can get to it another one dives into the pile, and quaffs the potion of invisibility/healing you desperately needed).