Jason, last year I threw a burger bar party for my daughter's birthday. I made a ton of topping combinations and did sliders. I had grilled pineapple, pastrami, sautéed mushrooms, bacon, Philly cheesesteak, Avocado, mac & cheese..... The combinations were left up to everyone's imagination and tastes. It was a big hit.
Oh, and I think my favorite was Philly cheesesteak heeped on my burger.