Re: Decisions decisions.
That's kind of a loaded question. The list will vary depending on how close you are to shore/help.
I personally carry:
Socket set
Screw driver set
Pliers
Zip Ties
Wire - can be stripped by pliers in a pinch
I should go buy a prop wrench at some point along with upgrading my tool set to be a little more complete - socket set is a cheapo Northern Tool set so my tools are limited. But on the other hand, how much dead weight do I really want to add to my boat right now? I'm usually within ear shot of shore and could swim there if need be. I also usually boat with family that have their own boats so a tow in is a phone call away.
If I were further from shore/help, my tool list would increase immensely. To give you an idea, here's what I carry in my tow vehicle:
*Complete tool set - pliers, sockets, pry bars, hex keys, etc.
*Trolly jack - for trailer and truck
*Star wheel
*Second 1/2" socket with extension, high impact 22mm socket for lug nuts, extra lug nuts (stockers as I run wheel locks on my rims)
*Extra long handle 3/8" socket drive
*Jumper cables - need to be upgraded to a better set
*4x4 post so that I'm not jacking on bare metal
*Wheel chocks
*2000lb cable puller
*Collapsable shovel - never know when you might need to dispose of a body

*Spare winch for boat trailer - my former boss broke mine on an outing so I now carry a spare at all times
*blanket
*tarp
*1" recovery rope
*associated fluids - wiper, 1qt oil, brake, etc.
*(2) different tow bars with 2" balls - different drops so I can tow trailers level
I need to purchase a jump pack at some point and keep it in there as I've had need of it a few times.