Simplest hash functions

What came to your mind when you read “hash functions” in the title? If you’re pragmatic, you probably remembered SHA-256 or MD5. Those are cryptographic hash functions, and they work fast and well for arbitrary inputs, even if they are supplied by malicious actors. Or at least they’re designed to. That’s the exact opposite of what I want to talk about. I want to talk about the cheapest, stupidest, most ridiculous hash functions you can get away with.