Bare Knuckle Bash-Ups Left and Right ... Fights at Hollywood Nightclubs!

L.A.'s known as the City of Angels ... but not everyone's so nice in this town!

There are always a few knuckleheads hanging out in the nightclubs lining the streets of Hollywood -- many of which don't even exist anymore ... and some of these folks didn't get the memo about asking questions first before throwing punches!

We've put together a timeline of dust-ups we've caught on camera in the past ... check it out just in case you need a refresher about how a fun night out can go south real fast.