Quark, because odds are, if you paid him enough, you're going to have a good time. Barclay is too much into pre-modern fantasy. The Doctor would probably involve a lot singing. Tom Paris is a close second because he tends to be modern and creative. groovy weapons-- in the 21 century, dealing with situations common today, would you rather have a hand phaser that stuns, an impenetrable personal force field, a personal cloaking device, or a personal transporter device?