R2-D2, BB-8 and Chopper all fall within this category of robotic, miniature mechanics. These droids are the Swiss Army knives of Star Wars. (I mean, they multiple appendages, tools, and of course plenty of attitude.) Neither the Rebels nor the Resistance would travel far without these little astro-droids performing repairs or calculating hyperspace jumps.
Usually reliable, we can thank R5-D4’s bad motivator for freeing R2 to finish his mission and deliver the stolen Death Star plans.