My mother's banana bread is my default Thing To Make whenever I throw a party or find myself in need of a hostess gift. It's quick, it's easy, and - best part - it can be personalized with the addition of things like nuts and Nutella. My mom has had this recipe for years - decades, I think; it's written down on a little index card in a box that she's had since high school - and it's never failed me (other than once, when I accidentally undercooked it and ended up with banana bread on the outside and banana soup on the inside; don't do that).
What you need:
1/2 cup softened butter