The Viper probe droid, also known as the probot (hello!), was a reconnaissance droid used by the Galactic Empire, most notably in the Battle of Hoth. It was a jellyfish looking dealie-bob that floated on repulsorlifts and mumbled to itself like Popeye.
The probe droid communicated its findings via a HoloNet transceiver. In its spare time, the droid used the HoloNet to surf droid porn. In fact, Viper probe droids were some of the most perverted artificial lifeforms in the galaxy, which is how they got their nickname "probot," for their deviant recreational activities performed on unsuspecting rural citizens of the galaxy. Other nicknames for the probot include the probinator, the proctobot, and the hideous metal monster that sticks things up your ass.
According to some video games, hundreds of probe droids fought in the Battle of Hoth. Yeah, they were just floating around the battlefield by the dozens, and snowspeeders shot them in the low levels, before eventually fighting AT-STs and AT-ATs. Why the Empire would deploy lightly armored probe droids to fight in their army, rather than normal battle droids or just more stormtroopers, is anyone's guess.
The name "Viper" came from an early probe droid prototype, which later became a window cleaner. "I am de viper," it proclaimed. "I haff come to vipe de vindows."