Rumsey Rum is a brand of several alcoholic beverages. Varieties include [Rumsey Rum], [Rumsey Rum Light], [Rumsey Rum Dark], and [Rumsey Rum Black Label].
In addition to getting you drunk, Rumsey Rums provide a "well fed" stamina bonus. The Stamina bonus will replace any "well fed" aura.
[Rumsey Rum] is a quest reward from  Whiskey Slim's Lost Grogω τ ϖ.
[Rumsey Rum Light], [Rumsey Rum Dark], and [Rumsey Rum Black Label] can be fished from Floating Wreckage.
[Rumsey Rum Black Label] can also be purchased at the inn in Southshore, in Old Hillsbrad Foothills. (Note that this is not Alliance only.)
The 'Rumsey Rum' brand was named after World of Warcraft's Lead Server Programmer, Joe Rumsey.