Tag up on that!

An expression used to claim ownership of something that is not and (potentially) never will be, yours, but is highly desirable. Examples may include a Ferrari, a super hot female, a mansion. Once something is "tagged up on", it cannot be tagged by a buddy, it is yours, forever...in fantasy land.

Dave: "Woah, check out the chick in the black bikini!"
Bob: "Yup, wow! Tag Up On That!"
Dave: "Aw, man! I was gonna ask her for her number too! Well, I guess she's yours now."