I could easily do without having some of these things in my kit, because of my equipment, preferences, and the type of diving I do.
spare fin straps - You shouldn't need these if you have spring straps.
defogger - spit works just as well, and takes up less space.
extra wt belt buckle - Probably not needed... I keep one because I have so many.
decongestant, dramamine/bonine/protien bar/bandaids/sunscreen/etc - I have a seperate first aid kit in the car that has all this stuff. I don't consider it part of my save-a-dive kit.
wrenches/toots/etc - I have an all-in-one scubatool that keeps everything I need handy, and saves a lot of space
DIN adapter - only handy if you use DIN
Spare reg - nice to have, but a bit bulky and expensive unless you already have an unused reg kicking around.
IP gauge, reg parts and hoses - great if you're accustomed to working on your regs at the beach. I'd rather do it at home in a clean environment, or have it serviced professionally.
HID battery fuses - Good if you have something that needs them.
Wingnuts - handy, but only if you dive with a backplate.
Money/phone card - good to have, but the denomination/form is up to you.
I'd add a sharp knife and some aquaseal to what you have there, but it seems otherwise like a good list. I left the remaining items below.
Of course, if you're good with duct tape, you could probably do without the mask strap, zip ties, knife straps, braided nylon, lanyard slides, and assorted connectors.
pkatzman once bubbled...
Looks like this is the list so far:
spare mask strap
o-rings
silicon grease
zip ties
money
plug for primary reg
batteries
spare reg mouthpiece
duct tape
mini maglight
knife straps
bolt snaps
lobster guage
#18 braided nylon
chem sticks
spare mask
pencil
sharpie
lanyard slides
rubber mallet
gear manuals