I usually make brownies with no frosting, but if I want something special I put Andes candies (the chocolate mint ones) on top of the brownies as soon as they come out of the oven. When the candy is all melted spread it over the top.
Depends. I prefer a rich chocolate and coffee flavoured frosting on brownies--but if you are serving brownies outside, and you have a forecast for a hot, hot day--omit frosting and serve with ice cream on top. Ice cream--the solution to everything!
Though, to be honest, I'll eat them with or without frosting, and pick the nuts out if I have to. But when I make them, I make them moist and chewy, with frosting... and no nuts. Cake-like brownies tend to taste a bit dry-ish to me.