Well since you are discussing tools other than just drills I'll pipe up about my Milwaukee screwdriver.
Milwaukee 0490-20 4 Volt Li-ion
Every time I use it I kick myself for only buying 5 (1 for me and one for each of my kids) of the drill w/ 2 batteries
and charger kits. I should have bought 2 dozen. As far as I know they are all still running and the batteries are still good. I used two of the sets in the last few months.
Lowes was selling them for $19.99 when they were first introduced. The batteries, like most Li-ion seem to last forever, and it has enough torque to twist my wrist. Then the price jumped to over $100.