I went through a handful of cordless drills before I found the Black and Decker LDX120C 20 Volt Lithium Ion drill. The drill is lightweight and the battery lasts a very long time - for my annual, I never have any fatigue in my hand and the battery lasts without needing any charging. The clutch system works flawlessly for automatically disengaging the drill once the proper torque has been achieved.
Amazon and Home Depot have it for around $55, and the reviews for the drill are in the 4.5+/5 stars range. The only regret about this drill I have is that I did not buy it during my build. I consider it my favorite tool now!
Since my purchase, Black and Decker has released a version with 2 speeds - the LDX220SB model (0-400/0-1400 RPM Settings). It goes for about $70 on Amazon. I haven't found the need for multiple speed settings for the one I have.