The marinade used in ceviche is citrus based, with lemons and limes being the most commonly used. This being said, all citrus will work. In addition to adding flavor, the citric acid causes the proteins in the seafood to become denatured which pickles or "cooks" the fish without heat.
This seems more of a summer dish, but I attended a themed cocktail party and this fit right in with the other Mexican dishes served.
2 each of the following (juice and zest):
1lb bay scallops
1 small red onion
1 small red bell pepper
2 cloves garlic, minced
1/2 c fresh cilantro, chopped
1/2 tbsp coarse sea salt2 tbsp extra virgin olive oil
Add all ingredients to a bowl and let marinade for 4-6 hours. Serve cold with tortillas.