HOT! List of PS2 Games: Buy Two Get One FREE @Toys R US!
 

Apparently, not all of the PS2 games are valid for the b2g1 free offer, thanks to YoshiFan for original post
It actually took me a few hours to dig out those games eligible for the offer while shopping at ToysRus for myself, so I've complied this list of PS2 games which are all eligible for the b2g1 free offer. Hopefully, it can help someone to save a lot of time. If I miss any, feel free to add your findings.

PS2 Game: Buy 2 Get 1 Free
Search for these games which are $49.99 each, choose any 3 games from the list,
then enter the b2g1 free code 906642 at the checkout to get 1 game free.
Grand Theft Auto: Vice City
TigerWoods 2003
Sega Sports NBA 2003
Sega Sports Tennis
Sega Sports NFL 2003
MLB Slugfest 2003
Hitman 2: Silent Assassin
NFS Hot Pursuit 2
Suikoden 3
Shinobi
Tony Hawk's Pro Skater 4
Onimusha 2
Grand Theft Auto 3
Red Faction II
Contra: Shattered Soldier
Lara Croft Tomb Raider: The Angel of Darkness
Spyro: Enter the Dragonfly
Kingdom Hearts
TimeSplitters 2
Virtua Fighter 4
WWE Smackdown! Shut Your Mouth
Burnout 2
Max Payne
Test Drive
Transworld Surf
Street Hoops
Medal of Honor Frontline
Metal Gear Solid 2: Sons of Liberty