Considering you guys are professionals and live or die by your tools, I am surprised no one has mentioned Festool. They are intelligent drivers and were the first brand to hit the market with 3-phase servo motors (brushless DC). The 3-stage planetary gearset is bullet-proof, and the internal electronics will protect both the motor and the battery from your abuse and mistakes. They have an unlimited 3-year warranty that even covers the batteries.
For example, as was already pointed out, never discharge the battery to 0% by tying the trigger on. The Festool drill monitors the battery life and shuts the drill down if the battery overheats, goes too far into the depleted range, or the motor current or motor temperature gets too high. If you try to take more juice out of the battery than the battery can safely deliver, it shuts down. For example, with a full battery, the drill will happily drive a 6 inch lag screw, but if the battery still has plenty of power for other tasks, but is down to say 10% capacity, the electronics won't let you over-tax the battery by trying to drive a huge lag screw, and shutting down and giving you an audible beep to tell you why it shut down.
On most drills, if you left them sitting out in the hot sun, their internal temperature would easily shoot up above 120 degrees before use, and when you used the drill, you would damage the motor and battery. The Festool drill monitors temperature and would not allow you to damage the drill even if you tried.
The original version of the drill is the C12, and has a C-handle design with either NiCd or NiMH batteries. I wrote a technical review for it a couple of years ago.
Festool C12 Technical Review.
The newest version is the T12 and T15 drills, and are a T-handle design and come with either NiCd, NiMH, or LiIon. Because of the greater efficiency of the 3-phase motor, these low voltage drills have more power than their higher voltage counterparts. The new T-class drills use a custom motor manufactured by Festool, which is so secret that only a couple of people at the company are permitted to enter the area where they are wound. (Normally Festool shows off their motor-line with pride, but these motors are wound in a secluding section of the factory.) The T-class drills come with the right-angle head, which would come in handy for drilling studs. It is not just a snap-on part, but locks to the drill housing in any position you want.
Oh, I almost forgot, but for me personally, I absolutely despise the "grinding" sound that a drill's clutch makes when it engages. The C12 drill has a sensor in the clutch so that when the clutch engages, the motor stops with just a single click of the clutch. The new T15 drill has an electronic clutch and is totally silent. When the motor current reaches the clutch set-point, the drill beeps and stops-no grinding sound!
C12 Drill: (with quick-change tip. The removable keyless chuck is shown below next to the picture of the T15. All chucks are interchangeable, quick-release and can be swapped out in less than 2 seconds. They include a standard chuck, right angle chuck, offset chuck--for getting in tight areas like next to a wall, and a drywall chuck.
T15 Drill:
I don't work for Festool, but I do some technical writing for them as a hobby.
