Coffiend
Noun: 1. Someone who drinks coffee like there is no tomorrow; 2. Someone who cannot function without coffee.
Person 1: Isn't that like your eleventh cup of coffee today??
Person 2: Twelfth.
Person 1: Dude. You're a coffiend.
Person 2: Twelfth.
Person 1: Dude. You're a coffiend.