This may help someone.
I keep a small container with:
screws (electrical panels),
driver bits (access panels),
hose caps (faucets, water heater drains, laundry)
band aids (me getting cut)
small screw drivers (tight areas)
Seems like the access panels and furnaces always have various screw heads.
This screw driver that cost $9.99 is a great tool, I use 4 rechargeable AA batteries, great life and another tip I just started to do is if you take out bit it can be used for a nut driver. (I have an assortment of those as well)
Hope it helps, it save me, like today!!