Although all UFOs used by the aliens of the First Alien War only needed a power source and navigation system for the bare bones(excluding the Small Scout for some reason), certain UFOs were fitted with special componets and machinery that is used for specific tasks. For example, a Harvester is fitted with surgical equipment for mutilating livestock and containers for storing harvested foodstuffs. Of course, X-Com could not use these in their own reverse-engineered UFOs, nor did they actually need to, but they were useful for earning extra cash by selling them on the Black Market.
The are as following
Alien Food: A truly alien foodstuff that is a nutrient soup created by dissoving mutilated cattle or even human body parts in a solvent. It is assumed that it is injected directly into the bloodstream of an alien.
Alien Entertainment: Though we wouldn think they take pleasure in punting X-Com soldiers, it turns out that even our alien enemies like to have fun every now and again. These strange wall panels that look like animated yellow and blue clouds are built with psionic circuitry that stimulates the pleasure centers of the brain, creating effects similar to hallucinogenic drugs(AKA Magic Mushrooms). These strange devices are the only evidence that the aliens have any form of culture.
Alien Surgery: A typical alien surgery equipment set includes an operating table, light plasma beams for incisions and storage containers for removed organs. These are usually used for mutilating livestock, particularly cows.
Examination Room: Found on Abductors, these chambers are used for performing insidious experiments on captured humans. Many are interrogated or mutilated, sometimes killed. Women are impregnated with alien foetuses, which are then extracted several months later. Besides whatever tools used in experiments, the room only consists of a simple operating table.