The most entertaining drunk I've seen to date would be a tough competition. As a solo, probably Rory, aka Squinn, aka Brian the Pink Shark from EoFF. As a duet, Jess and smittenkitten. ;D
I have videos of all sorts of drunken antics by EoFFers, but, sadly, some of them have been lost to poor encryption (my favourite video), while others are, uh, involving me. Which I'm not going to put on EoFF. So yeah. xD
Drunken singing is my favourite thing when with a bunch of friends.