Series of tools daily for working on boats. It has perhaps the best form factor for tight spots and hands down has the widest selection of tools too choose from. The batteries last longer than my old DeWalt 18V stuff and I have not been able to break a single one of the tools or kill a single battery. I particularly like the right angle drill but there is not a tool in the M12 series I have not been pleased with..

I use:

Two M12 3/8" Drills
M12 Impact Driver
M12 Screw Gun
M12 Multi-Master
M12 Dremel
M12 LED Work Light
M12 Jig Saw
M12 Hackzall
M12 Right Angle Drill
M12 PEX Expander
M12 3/8" Ratchet

Most of these tools plus about 12 batteries fit in a fairly small tool bag.... The only tools I don't lug along daily would be the hackzall, jig saw and PEX expander. On the boat I am on now my LED work light has been going for three straight days on the same battery.

I would urge staying away from the new Porter Cable cordless stuff, it is pure JUNK.. I bought an 18V kit and my little M12 stuff kicks its butt all over the place..... Sad to see Porter Cable suffer from CCS / Chinese crap syndrome.. Even my Ryobi is head and shoulders better than the new Porter Cable JUNK...... Sad because they used to build great stuff. My Porter Cable router is now almost 40 years old. It was my dad's and is still going strong. I highly doubt any of my current electrically powered tools other than Fein or Festool, will still be going in 40 years....