My plane is severely limited in cargo volume (not so much weight) and as a result, I try to brings things that can serve several purposes. Here's some of my multipurpose tools.
Similar to other posts on the preheater thread, I'm using an aluminum dryer vent to get heat into my engine. The difference is that it is also my cook stove. The MSR firefly is a light weight stove that is great for cooking and can get the engine warm in about a half hour when the temps are around 15-25 F. If it's colder than that I'm gonna stay in the sack.
Another multiuse device is my surplus shovel. I sharpened one side so it can be used for a half-assed axe. I wouldn't want to chop trees down with it, but I can easily cut brances for a fire or tent poles. I lengthened the handle so it can also be used to support the plane while fixing flat tires. To do this I use a wire run through a hole drilled in the end of the handle to loosely hold the shovel in place.
Then I lift at the strut attach points to lift the plane high enough that the shovel swings under the gear leg and is in place to support the plane.
With the shovel tightened at 90 degrees, it will support my wee little plane even on soft ground.
I'd like to hear about more home grown multipurpose equipment.