Marinate the Shrimp:

1. In a large zip-seal plastic bag, combine the tequila, jalapeno and salt. Zest and juice the lemon and lime, and add to the marinade. Add shrimp. Seal the bag closed and shake to evenly coat the shrimp with marinade. Transfer to the refrigerator, and marinate for at least 30 minutes. (Warning! Do not marinate for more than one hour - any longer, and the acid from the citrus will begin turning the shrimp to ceviche).

Grill the Avocados and Shrimp:

1. Meanwhile, preheat a gas or charcoal grill on low heat. Lightly oil the grate.
2. Halve each avocado lengthwise. Remove and discard the pit. Lightly oil the cut surfaces.
3. Arrange the avocado halves cut side down on preheated grill. Cover and grill for about 3-5 minutes, just long enough to char marks on the avocado flesh. Transfer to a platter and set aside to cool.
4. Turn up the heat on the grill to high, and lightly oil the grate again.
5. Remove shrimp from the the marinade and arrange on the grill. Discard the marinade. Cook shrimp for about 2-3 minutes per side, or until bright pink and opaque. Transfer to a platter, and set aside until ready to assemble the cocktails.

Prepare the Guacamole:

1. When ready to serve, prepare the guacamole. Using a fork, scoop the avocado flesh into a mixing bowl, and mash until slightly chunky (or until completely smooth, depending on your preference). Stir in onion, garlic, jalapeno, cilantro, lime juice and salt. Add tomato, if using.
2. To assemble the cocktails, spoon the guacamole into four martini glasses, then dangle four shrimps from the rim of each glass. Serve with a basket of tortilla chips and extra lime wedges.