A lot of GameStops are doing the 50% off sticker thing it seems. Just yesterday I went to GameStop and picked up the PS2 and Xbox versions of Driv3r (the PS2 version for my nephew, Xbox ver. for me) for 50% off each one. It's not a great game, but for $10, it's pretty cool. My nephew loves games like this, so I know he'll enjoy it. There was a lot of other games too for 50% off (Maximo Vs. AoZ, Front Mission 4, some other cool titles I already have (or are going to get for Christmas)).
The only snag: while these are "new", they're the floor models (ie- the case is already been unwrapped so it can be displayed sans disc, essentially making it "used" anyway :\).
Still, for 50% regular price, it's definitely worth looking into. I didn't see any strategy guides with the sticker on them though. I never thought about it. >_