It's random which ones will show up in the shop on any given day. Sometimes the randomness brings unfortunate outcomes. Have you done all of Isabelle's introductory/tutorial chores? It is possible to get a fishing pole from her if you haven't gotten a bug net out of her already. She also gave me a watering can through the course of her chores. From my experience with Animal Crossing in general, axes and slingshots seem to show up in the shop less often than the other tools. You can always upgrade the shop by making transactions there and then they will sell more tools each day so your chances will be greater! Or if you have wifi friends, they might be able to help you out!It's been 4 or 5 days and the store hasn't yet changed them out.
How do I get a fishing pole, axe, or slingshot?
I'm pretty sure you get the wet suit at the island.
Other animals buy things you put on sale (Drago bought my clock!)
It's so neat when you are in Re-Tail browsing or putting stuff up and a villager comes in and asks if he should buy your item!
Makes the game seem more alive when you actually see them doing things