Here's what you NEED:
-Life jackets (AND a type IV throwable cushion. I recommend tying 50' of cord or rope to it.)
-First Aid Kit
-VHF Radio (at least handheld. Some will say its not NEEDED, but i disagree)
-Anchor. I personally like the 12# Navy anchor. Some are coated in rubber
-6' of 1/4" chain for the anchor
-At LEAST 50' of 3/8" 3 strand nylon anchor rode. 100' or more is better
-Quart of oil
-Quart of lower unit oil
-Chart of Winni (We have both Duncan and Bizer)
-Extra cash on board
-Leatherman or a multitool. Just trust me.

-Fire extinguisher. I'd get two.
-Dock line. The rule of thumb is the length should be as long as the boat. So you want four 20' of 3/8 dock line.
-Spare fuses
-Spare bulb for running lights
Here's what you might WANT:
-1 million+ candlepower flashlight
-Flare kit
-Compass
-Fenders
-Spring lines (same dimensions as dock lines, just get 2 or 4 more)
-Other spare parts: bolts, prop nut, washer, etc
-Spare prop
-Cooler with lots of water
-Boat hook
-Orange flag (if you tow skiers or tubers)
-Diver down flag
-Extra sunglasses with UV protection
-Sunblock
-Second smaller anchor with 50' of 1/4" or 5/16" 3 strand rode.
-Sea Tow or BoatUS membership
That's all I can think of. You can get ALL of this at Parafunalia in Gilford. Great people.
I know it seems like a lot of stuff, but much of it is required by law. I say just get it all. "If you need it and you don't have it, you sing a different tune."
Questions, just ask. Good luck!
Edit: whoever asked about a tow rope: Sea Tow or Tow BoatUS will have a tow rope. But if you want one for towing, make sure it is around 50' and at LEAST 3/8" THREE STRAND NYLON (this is for a 19' boat). Nylon is able to stretch so your fittings won't be blown when the boat goes over waves. Also do not tow over headway speed.