Winkles Old Peculiar
Ankh-Morpork's favorite and signature beer (brewed with the flavorful and nutritious waters of the River Ankh). It even enjoyed a brief vogue among the aristocracy when Earl de Nobbes introduced them to it in Feet of Clay. It is also enjoyed by the Wizards of the Unseen University.
Roundworld has Theakston's Old Peculier (note spelling), brewed in North Yorkshire.