Bartender

A bartender (or a barkeeper and barserver) is an NPC which sells alcoholic beverages, that can make players who drink too much of them Tipsy, Drunk, or even Totally Smashed. These effects cause blurred vision and difficulty with moving in straight lines, becoming more severe with each tier of drunkenness. Being totally smashed can cause the player to vomit.

For more information, see Tipsy and Drunk.

Bartender is also the name for for a popular add-on which allows the player to move, resize and otherwise adjust their action bars on the screen.