No matter how old you are, you look like you're going down on a robot. But if you're old enough to remember smoking real cigarettes in a bar, you shouldn't be blowing out a big pink cloud of Hawaiian punch-scented vape juice.
Take a bunch of selfies
One shot for the ol' memory bank is fine (but questionable). But nobody wants to see you duck-lipsing in front of every single drink, especially when your pursed lips make your face look like a football left out in the rain.
Argue with a significant other
Especially if it's somebody else's significant other. But if it's your own and you're in a long-term relationship, the mature thing to do is to save your argument for the Uber ride home. You don't have to tip that guy for enduring your hissing whisper fight, but you do have to tip the bartender.
Dance on the bar
Just because you have fond memories of Coyote Ugly being a thing doesn't mean anyone else does.
Order a shot containing more than one ingredient
If there's a single gray hair on your body, you should not be asking for some cutesy shot. If you insist, the smart thing to do is order a shot of each individual liquor for the table, then go mix your own Slippery Chundlefart shot in the bathroom so nobody can see. Or, you know, get whiskey or tequila like a quasi-grown-up.
Stiff the bartender
There's a special place in hell for people who do this. And there's an even worse circle reserved for people who do it despite having a 401k.
Drink anything out of a test tube
Come on. You're not at a foam party, are you?! Get your shit together!
Arm wrestle someone for custody of your child
Fine, Stallone can get away with this still. But no one else. Got it? NO ONE ELSE!