1) I'm pretty sure the consensus is on "a camera" as the first thing we'd choose to bring with us, but allow me to get specific here and go for "the best high-definition video camera unit available". If you think Kaguya looked great from dozens of miles up in orbit, imagine having one of those babies on the lunar surface with free EVAs to play with?
2) A ground vehicle. I'm not getting stuck walking around a LM for all that time with nothing to do but lope around nearby craters; I want to cover some serious mileage. And since this is a short-term stay I'll forego the later concept vehicles and just take an old Apollo-era rover, which remains the Ultimate 4x4 (you can't get any more "off-road" than the Moon).
3) I want to travel 200,000 miles across the emptiness of space; make a soft landing on Earth's only satellite; egress from the spacecraft; travel about 25km out into the lonely expanse of lunar dust where no human has ever ventured -- indeed, where there hasn't been any activity of any kind, except for the occasional micrometeroid impact, for literally two billion years; reach into a utility pack on the side of my PLSS; and, while standing in the silent lunar vacuum that is as old as time itself, gently deposit...
... a Smurf doll.