I bought one of the new porter cable 19v kits that lowes has on sale every now and then. 19v reciprocating saw, drill, flashlight and circular saw in a duffel bag. I've added a jigsaw and want to add a couple more tools. Bought an assortment of drill/screwdriver bits, jog saw blades and reciprocating saw blades and keep them in there, then a couple boxes of screws of various lengths, construction or decking. If you have to put something back together or cover something with plywood so construction screws will be very handy, keep them right there with the drill/driver.
I have a weekly reminder to charge batteries, I charge my electric razor and items that get used inside the house and stick one of the batteries in the drill charger then too so I make sure they are always topped off if I should need them.