World of Warcraft players are fond of commenting on the fact that the wolf they just killed was somehow carrying a glass of ice-cold milk. How did they keep from spilling it?
Most games that implement random loot also include a system for generating equipment with randomized effects and bonuses, such as armor that increases resistance to certain elements. The actual usefulness of such equipment varies greatly, as it is entirely possible to come across an item with bonuses that do not correspond with each other at all (such as granting bonuses to two skills that are very unlikely to be used by the same character). Conversely, there is the rare randomly generated item that grants bonuses with a synergistic quality - for example, increasing combat skills and strength, making your attacks both more effective and more damaging.
Of course, even items with useless bonuses might still sell for lots of money to in-game vendors.