Cajun Seafood Crackers is a simple appetizer that I love.

Your choice of crackers, I prefer plain old saltines.
1 large onion quartered
1 qt. water
1 tbs. liquid crab boil
2 tsp. creole seasoning
1 lb crawfish, shrimp or crab meat (cooked)
Thinly sliced smoked sausage
Sliced jalapenos (optional)
Seafood Dipping Sauce

Boil onion in water and creole seasoning until tender. Turn off fire and add liquid crab boil, let sit for about five minutes. Remove the onion and let cool to handling temperature. Gently separate onion slices and cut them to a size that will fit the crackers. Lay onions on paper towels to dry them a little round side down. Place a baking pan on top of them and let them cool several minutes. Now you can add the shrimp or crawfish  to the pot unless they are from a seafood boil since they would be seasoned already. In that case just gently warm them. Do the same thing with the sausage.  (season the crab meat like this. )  Let the seafood sit in the pot a few minutes and taste.

Lay crackers on a serving tray. Put a slice of onion on each cracker round side down. Put a pinch of creole seasoning on each onion. Spoon a little Seafood dipping sauce on each onion [the onion will help insulate the sauce from the cracker so the cracker won't get soggy too fast]. Place a slice of sausage. Place a few shrimp, crawfish or some crab meat on each. Place a slice of jalapeno on each (optional). 

Note: Do different combinations leaving out the sausage, seafood and/or jalapenos.