Bosch
I've owned the Bosch PS20-2 driver for a year now. It's the best driver I've ever owned (and I've owned/still own several, including Makita, Dewalt, Craftsman, etc.).
-It's a driver, not a drill per se (no chuck, just a quick release for driver bits), but Bosch sells a small accessory chuck if you need one.
-It's small enough to fit in a pocket/tool pouch.
-Pistol grip is comfortable enough to use all day.
-Much lighter than other drivers I own.
-Plenty of power; it spins at a relatively low speed with loads of torque.
-The batteries last a long time-I've driven over 100 3" deck screws on one battery charge with this little guy (also deburred every hole in the emp kit with two battery charges).
-Trigger 'teases' well enough for deburring. A light touch spins the Cleaveland deburring bit one turn.
-The batteries recharge quickly (<30 min).
-It has an LED light for the work
-More expensive than some other brands (about $115 with two batteries, charger and nylon case)...but I think this is definitely a case of getting value for your $$.
Bosch also makes a right angle model (PS10-2; about $123).
Mike