Tres Generaciones by Sauza is my favorite
There is more than one Tres Generaciones so make sure you get the Gold Anejo (it comes in a dark stuby bottle with a cork). I found this stuff a few years ago when I was in search of "the best tequilla". I read in a bar guide that there are three major things to look at when searching for a tequilla:
1. That it is made from 100% agave fruit
2. That it is anejo or aged for 3 years or longer (not positive on the # of years)
3. That it is gold or rosado (aged in oak and spice added for flavor and color)
Of course there are a lot of tequillas that fit this description but it's a good place to start. Here's a good website for info on high end liquors (cigars too)
Mission Liquors
Hope this helps
Scott