Potato and cheese is classic, and honestly it hits the spot better than you might expect. Toss with butter after boiling. Keeps them from sticking and tastes great.
Commonly topped with sour cream, green onions, other onions, and/or bacon depending on what you have handy. A nice fatty sour cream with grilled yellow onions is my favourite, especially served with a nice hunk of garlic sausage.
I find pan frying them works best if they're leftovers, the dough fries up better after it's boiled and then dried out a little. It's a very good option for sure.