Meatballs, buffalo wings, mac and cheese, jambalaya. Lots of possibilities once you really think about it and then do the research. Good luck.

Stuffed grape leaves are very yummy when made in a slow cooker.

if your guests aren't opposed to some assembly required dishes you can roast some pulled pork in a slow cooker and then arrange it with some toppings for the guests to assemble tacos or sliders!

http://chaosinthekitchen.com/2010/08/crockpot-root-beer-pulled-pork-sliders/
http://www.eatlivetravelwrite.com/2011/03/kitchen-bootcamp-world-cuisines/

I've done meatballs quite often as a appetizer in my slow cooker. You can also do cocktail sausages as well. http://www.bhg.com/recipe/pork/bourbon-glazed-cocktail-sausages/

Otherwise, you can also use you cooker as a buffet warmer and place items you've cooked ahead of time in the slow cooker on the warm setting to stay warm without having to juggle serving and entertaining.

Spinach and Artichoke dip (or any other hot dip), or use small glassware or Dixie cups and have soup or soup shots.

Ditto to the above on soup shots! Stephanie O'Dea has a good one. And Party City sells little plastic glasses.

Reuben dip. It's delicious. I made mine with sauteed mushrooms because I'm vegetarian.

8 ounces finely diced corned beef or sautéed button mushrooms
8 ounces cream cheese
4 ounces sauerkraut, rinsed and drained (Squeeze it in a tea towel)
1 1/2 cups shredded Swiss cheese
1/2 cup Thousand Island dressing

Mix it up and put it on low in the crock pot for an hour or so before the party starts. Serve with rye crackers or those teeny little pumpernickel breads.

Meatballs are for sure always the fastest item to go when I serve them.

Outrageous Warm Chicken Nacho Dip

Turkey Meatballs with Cranberry Sauce

Cinnamon Almonds

Slow Cooker Chex Mix

You could always convert a non-crock pot recipe to the crock pot.
Hot Blueberry Cheddar Dip served with sturdy crackers instead of toasted bread. Adjust the recipe for your size of crock pot and number of guests

Soups are another popular option. Offer the tasting cups or whatever they are called with some small sauce ladles to pour the soups into the cups.

Our extended family offered chips with crock pot sausage queso dip for many years.

sweet and spicy kielbasa - slice up the kielbasa into coins, plop it into the slowcooker with your choice of chili sauce (my family swears by heinz, but make your own if you're inspired), and whole cranberry sauce or chutney, relish, etc. Serve toothpicks alongside, you won't even need plates!

3 ingredients, huge crowd pleaser.

Beer Balls! Not the classiest name but they are awesome!!!

http://www.grouprecipes.com/9101/cocktail-beer-balls.html

this dip is kind of of pedestrian, but i've had it at a few different parties this season and it is SO good, and goes so fast. serve with celery sticks, crackers, and/or nachos. http://allrecipes.com/recipe/buffalo-chicken-dip/