Jack Osbourne's Ex -- Pretty, Dangerous?

6/4/2010 6:45 PM PDT
Jack Osbourne's 24-year-old ex-girlfriend Niki Cloyd -- the one who allegedly keyed the hell out of his Aston Martin -- finally surfaced in L.A. today where she proved one very important fact ... she's hot.

As TMZ first reported, Jack filed documents in L.A. County Superior Court yesterday in an effort to get a restraining order against Cloyd ... but the judge ultimately rejected his request.

He might be the only person who wants to keep Niki away.