In my opinion, there is nothing better than fresh Pico De Gallo. I can eat it straight with a spoon and when I top a taco with it - watch out, I put ridiculous amounts on. You can vary this recipe with your favorite type of onion, pepper, etc, add more of what you like and less of what you don't, etc. This with some baked tortilla chips is one of my very favorite snacks there is.
6 roma tomatoes
2 halepeno peppers (sliced, seeds removed and finely diced)
1 white onion
1 bunch cilantro
1 garlic clove
juice of 1 lime
Chop all veggies, toss together with garlic, salt and lime juice. If you want it hotter, keep some seeds from the halepeno. When removing seeds, either wear gloves or be very careful - they are hot. Salt to taste.
Now for a little tip. My mom taught me how to chop onions and now I think they are so fun to chop. Here is a wordless photo tutorial. And one for getting your tomatoes nice and uniform.