Erik, my mom makes these a lot. She uses the pre-made cookie crusts you can get in the baking aisle rather than making her own, but she's done all sorts of combinations. She usually uses the oreo, chocolate wafer or shortbread crusts, spreads a layer of icecream topping on the crust (fudge, strawberry, caramel, etc), chills that , then adds softened ice cream. Then she'll top with additional topping and freeze. Like I said, the sky's the limit with flavor combos, but some of my favorites are:
Butter crust:
caramel and prailine pecan ice cream or butter pecan
strawberry topping and strawberry cheesecake ice cream
pineapple topping and coconut or tropical fruit flavored sorbet or ice cream
Chocolate crusts:
cookies and cream ice cream and hot fudge
chocolate brownie ice cream and peanut butter topping
chocolate chip cookie dough ice cream and hot fudge
mint chocolate chip ice cream and hot fudge (this is really good in the oreo crust!)