Acronym: Bring Your Own Beer. A party where the alcohol is not provided.

Bring your own Burrito,

used for hardcore mexican parties.

Bring your own beer, booze, bitch, and/or bombs.

Bring your own Bible. Used by hardcore Christian kids.

Bring Yer Own Buzz
Battle Yer Own Beef
Bounce Yer Own Boobies
Bend Yer Own Barricades
Blaze Yer Own Barby
Beat Yer Own Boredom
Banish Yer Own Beasts
Bury Yer Own Bigotry
Be Yer Own Boss
Believe Yer Own Bullshit
Blend Yer Own Beverage
Blur Yer Own Boundaries
Bust Yer Own Balls
Butter Yer Own Bread
Burst Yer Own Bubble
Burn Yer Own Braincells
Build Yer Own Bridges
Birth Yer Own Beliefs
Bless Yer Own Brethren
Become Yer Own Buddah

Bring Your Own Bombs

Bring your own *insert "B" noun here*.
However, I have seen people insert non-B words, because people really are stupid.