Here's a random tequila-based old-fashioned cocktail, named after the origin of the spirit.
2 1/4 oz aged tequila (I used El Mayor Anejo; another anejo or even a good resposado would be nice too)
1/4 oz creme de cacao
1 dash Regan's #6 Orange Bitters
1 dash Bitter Truth Jerry Thomas' Own Decanter bitters (which I'm sadly having trouble finding now...)
1 dash apple bitters (homemade as previously covered)
Stir and strain over a large cube, blissfully ungarnished.