Obviously you can use it with Cool Whip and various frostings for desserts. Other uses include making deviled eggs, filling stuffed shells or other types of pasta, using it for twice baked potatoes, filling homemade donuts. I know there's more, but I can't think of them right now. I've used them for deviled eggs, but never twice baked potatoes. I use it all the time for desserts. It's a fun little tool!
I've been practicing some recipes this week (ss1)- I made the Crostinis (tapas) in the Season's Best Cookbook, and instead of spreading the cheese mixture on the bread slices, I used the Easy Accent Decorator- you have to use the largest opening attachment. They looked much prettier than the ones I just spread the cheese on.