My fave is a type of pico
de gallo (sp?). Though I've never measured amounts.
Use the following fresh vegetables to taste:
tomatoes
onions
jalepenos
cilantro (a big favorite of mine - and it helps pull mercury from the body, too!)
(optional):
tomatillos
mango
bell peppers
fresh corn
Then add lots of fresh lime juice. Lots.
Salt.
This is usually good for me. Most folks like to add some vinegar (red wine vinegar is good) and/or a bit of sugar.
Especially yummy mixed half and half with cooked black beans as a dip.