Lots of boyfriends have a hard time picking out gifts their girlfriends actually like. But Hills star Brody Jenner is going the safe route — diamonds. When asked about the most creative gift he's ever given at the Z100 Jingle Ball on Friday, he replied, "I can't tell you because I'm giving it to my girlfriend." But then told us anyway: "It's pretty good — it has diamonds in it, and it has pink diamonds in it. It's very creative — gonna mean a lot to her … I had to be all shady behind her back and talk to her friends." Was there a glue gun involved? "No glue gun, professional stone-setters." Whew.