A recipe from a MATE
4 Ripe Avocados- sliced
1 lime
1 Sweet onion
A bunch of Cilantro
Diced Grape Tomatoes
And Salt to taste....
Using a mortar and pesto- Crush the onions and Cilantro, together. Add a little salt, then crush in the  avocados. Stir in the tomotoes and cilantro. then add more salt and lime for taste.... Serve with corn chips
The Danny Doyle Guacamole recipe! 
2 Avocado
1/2 Small RED Onion diced small
1 Clove Garlic minced
1 Tomato diced
1 Fresh Lime squeezed
and a pinch of Kosher Salt

An Aussie Version
I have a yummy pea Guacamole recipe: blend 350g defrosted frozen peas, 1 garlic clove crushed, 2 chopped spring onions, 1tsp grated rind and juice of 1 lime, 1/2 tsp ground Cummin, 1 tbsp extra virgin olive oil, and a dash of Tabasco sauce (process till smooth). Add 2 tbsp chopped fresh coriander process for a few more seconds. Cover and Chill for 30 min. Sprinkle cayenne pepper over the top. Yummy with crudités or on rosemary and pinenut loaf.

Guacomole left overs- RARE but it could happen...Check out Emily's solution...

Martha's Version
2-3 Ripe Avocados
1 Tomato
1 Onion (small to medium)
A Large handful of fresh Cilantro, chopped
1/2  Lime
Salt and Pepper to taste

Halve the avocados lengthwise, take the pit out and use a knife to dice the avocado up while it's still in the skin.  Use a spoon to scrape that green goodness into a big bowl.  Dice the tomato and onion, add to big bowl.  Make sure you remove the stems from the cilantro first and just chop up the leaves and add as much as you like to the big bowl.  Using a fork, start mashing up the avocado and mixing up the ingredients.  Squeeze the fresh lime juice on top and add plenty of salt and pepper to taste.  
(Click to link to photos.)