Ryobi is a trusted brand, cheap but works (and quite good) for most DIYers:
this is the best deal, but seems out of stock online. you may check in your local store and use the 10% off coupon from Lowes:
http://www.homedepot.com/h_d1/
this one fits many starters:
http://www.homedepot.com/h_d1/
Or search P894 to see more choices, P894 is the most worthy combo from Ryobi. All Ryobi 18V tools can use Lithium Ion or NiCd batteries.
You can order online, free shipping. And call later (800-430-3376) to apply the Lowes 10% off coupon (they will just apply, without confirming whether you really have that coupon or not), don't use any other coupon---they will deny a 2nd coupon or reverse.