I have been using this kit for a few years and I am a fan:
ExpressTools.com: Makita LCT207W 12V max Lithium-Ion Cordless 2-Pc. Combo Kit
Small, lightweight, continuously rechargeable, I rebuilt my wood deck last year, change tires, run drywall screws all the time. I still own one of the original 9.6v greenie drill/drivers and the new Li/ion kit is better.