My sister and i are debating...is it possible to give yourself a black eyeand if so, how?

Walk yourself into a door, bang your head on a table, something like that.

yes u can easily give urself a black eye by punching yourself in the eye. if you are weak u may need to give yourself a few shots in the eye. word to your mother.

drink alot of alcohol, come to and wala black eyes,tattoos,new spouse,dented up vehicle,broken nose,missing teeth,scars and bruses,and STDs

Put a big rock in a small cloth sack, tie the sack, then swing the sack right in toward your eye. OUCH!!!

Figuratively, by making such a fool of yourself in public, you can be said to have given yourself a "black eye".
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Literally, by colliding with something very close to your eye, causing the surrounding tissues to bruise. This could be from a fall where you land on your face, to an auto accident where your face hits the steering wheel or is hit by the airbag. Lots of ways to give yourself a literal black eye, none of them comfortable.

If you get a black eye by having someone punch you in the eye, what if you got something shaped like a fist, and headbutted it so that your eye hit it. I think you could.

however, DO NOT TRY THIS, EVER!!!