If you're looking for some just to do shots, then you should go with the gold stuff, but if you want to make mixed drinks then get the clear stuff. At least that's what the guy in Mexico explained to me when I was there. I ended up buying some clear stuff as my shooter days are over.
I pretty much agree with that sentiment.
Patron, Sauza, Cuervo (and others) - all are/can be good.
I usually make margarita's when I'm in the mood. I prefer using extra lime juice (with triple sec or another similar mixer) then the traditional mixers that are sour/bitter. One can get away with this easier if you choose better 100% blue agave tequila. That bottle of Sauza (three generations) that someone (Redeye I think) brought to TR BBQ #1 a couple years ago was fantastic - still have some left. For a really good bottle, be prepared to spend $30-50.
Never aquired the taste for Mezcal personally. "Eat the worm dude" What the different variations mean:
plata or blanca ("silver" – aged no more than a couple of months)
oro or joven abocado ("gold" or "bottled when young" – "silver" tequila colored to resemble aged tequila)
reposado ("rested" – aged about a year)
añejo ("aged" or "vintage" – aged from 1 to 3 years)