If Rihanna can hang her hat on one thing, its her unpredictability.

She proved that once again as she walked into the Shamrock Social Club in Los Angeles and got "THUG LIFE" tatted on her knuckles.

When she hit Twitter with the pictures, things got a little heated.

Rihanna put up the pictures with the message, "All these b*tches screaming that 2pac back ? #THUGLIFE."

Some of her followers were less than thrilled:

The thing that I like most about Rihanna is she doesn't answer to anyone but herself.  She has a bagillion Twitter followers, and still takes the time to call out one of them for talking 'ish to her.

From her pictures it looked like she was getting another tattoo on her backside, but no word on what it is.

I'm guessing that it's my high school yearbook picture, you know . . . just because.