I'm going on a cruise, what should I bring?

We’re going on a cruise soon and I’ve never been. It’s a short one, 4 nights to the Bahamas. When we vacation, we normally pack what we think we’ll need and say “Walmart will have whatever we forgot,” but in this case, we’ll be stuck on the boat. There’s a ton of websites out there that have lists of suggested items, but I can’t tell if they’re just trying to sell crap or if we’ll actually need it all.
So, I ask the community… On your first cruise, what did you bring (or forget to bring) that made your experience that much better?