C-3PO is a protocol droid built by Anakin Skywalker that feared adventure and preferred etiquette and diplomacy. He and his lifelong droid friend R2-D2 pair up often as unlikely heroes of the Rebellion.
FX-7 was a medical assistant droid stationed with the Rebellion on Hoth's Echo base. He assisted 2-1B in healing Luke Skywalker's wampa wounds.
The hovering interrogator droid is known by its dark spherical shape bristling with torture devices. The mere sight of one often gets a full confession from its victims.
Cheap and expendable pit droids repair Podracers, sometimes not even waiting for the racer to go into the pit. When not in use, pit droids can fold up out of the way.
Something beyond the standard astromech droid, R2-D2 is a clever mechanic and pilot's aid, boasting an impressive array of special tools. He formed an unlikely friendship with the protocol droid C-3PO and became a hero to the Rebels.
R5-D4 is a standard astromech droid, used for the maintenance and repair of starships and as an interface between computers and humans.