This is CRAZY!

Tyga apparently had a beef with someone at Floyd Mayweather's 42nd birthday party at Sunset Room in Hollywood last night so he was escorted out. But the WILD thing is that as Tyga's fighting with the security guard and a rep from the club comes out and tells the rapper to leave, Tyga GRABS FOR THE SECURITY GUARD'S GUN!!! WTF?!

Kylie Jenner's ex actually puts his hands on the dude's holster and appears to try to grab the gun, while the security guard stays calm, pushes Tyga's hand away and makes sure his weapon is secure.

This could have turned into a HUGE mess -- and Tyga could have gotten in trouble for reaching for the guard's piece. He's lucky the dude was calm and collected.

Meanwhile, the party went on without Tyga, of course. When the birthday boy arrived, he showed off his Dapper Dan Gucci leather bomber jacket as he stepped out of his 1990s-era Mercedes. Bro went all out with the 90s theme! His pal French Montana arrived in a pimp-style fur coat and besides Tyga's little "incident" it looked like a pretty fun night.