Cashier, gesturing to a spiky orange fruit – “do you know what this is and the price of it?”
Me – “I have no idea. I thought it was pretty. I want to photograph it.”
Turns out to be a Kiwano Melon. Also known as the Horned Melon, the melano, the African horned cucumber, the jelly melon, and the hedged gourd. According to the Internet, it tastes like a combination of cucumbers, kiwis, and bananas.