Take a shot whenever Handsome Jack calls to insult you.
Take a shot whenever someone named and important gets slagged.
Take a shot whenever you set an enemy on fire only to have it wear off when they're just one hit point away from death.
Take a sip, or a shot if you're feeling suicidal, every time Handsome Jack has a Kick the Dog moment.
Take a sip every time you miss a point blank shot as Gaige because your accuracy is shot to hell after racking up hundreds of Anarchy stacks.
Question: Are you TRYING to kill us?
Take a sip whenever Moxxi makes an innuendo.
You may want to have an ambulance on standby for this one.
For Kreig players: Take a sip every time you use your action skill.
Take a sip every time Silence The Voices causes you to hit yourself in the face. Take a shot if it hits you more than twice in a row, 1-in-8 chance of self-injury be damned. Just chug if it's more than three times in a row, you'll probably need it.
Gunzerkers: Take a sip every time you accidentally start Gunzerking with a weapon combination you didn't mean to bring out, like a Dahl sniper rifle and a Hyperion pistol.