I think some specifics are in order when you ask open ended questions like this...
TF2 and L4D2 aren't very demanding games. I can play them quite easily with med-hi settings on 3-4 year old laptops.
What specifically are you going to use it for? How much do you want to spend...if the budget is tight, you can get a decent notebook from 350 to 500. If you want a graphics card added, it jumps to about 600-700. And - on up from there.
Refurbs are on sale right now at Dell(25% off), there are also major sales going on with the Lenovo's too(check SlickDeals). I personally bought a 3rd Gen Core i3 15.6 Inspiron this weekend for 330. The little lady will be pleased, it has a pink lid...