Here is my list additional to the requierements:
First aid kit
Spare horn or whistle
Pocket knife
Handheld VHF
Water
Spare clothing
Foul weather clothing
Flashlights
Extra
lines
Anchor and ride
Battery and manual operated
pumps
Blankets
Fishing pole
Quick repair equipment (sea cocks, tools, quick cure
epoxy, caulk etc)
Spare 1gal
fuel
A dc/ac power pack
Battery operated nav
lights
Dining stuff
Dry ice and a regular ice block
Cooler
Canned and dried foods (Dried figs, beef, fish, rice and pasta are always aboard)
Additional drinks (beer, wine etc.)
Books
Spare
fuel line
WD40
All those for a day out... Because if something is gonna happen it's gonna happen when you are not ready it... (murphy's law)