Smart Kitty

I'm thinking Hadley is one smart little kitty! She learns fast and I've taught her to shake & "give me 5"...so I was wondering what other tricks I could teach her. Any suggestions? I know you're supposed to teach them things they are already good at. (She was always pawing at me and reaching for me, so that's why I taught her that trick.) Lately when you try to walk into a room, she runs in front of you and jumps straight up and grabs the door knob with both paws. She'll hang there a few seconds waiting on you to open the door. I'm not too sure I want to turn that into a trick though! LOL!! I'd love some suggestions...never really trained a kitty before!!