Gran Turismo 3: A-Spec is only $20, so you should buy that.
Twisted Metal: Black is only $20 too, so you should also buy that.
Virtua Fighter 4 is pretty tight if you're into fighting games, which I am.
I'm a big fan of Metal Gear Solid, so the sequel was a "must own" for me.
Check out
http://ps2.ign.com - basically, anything they give an 8.5 or higher under their "reviews" category is worth owning. Some that are below 8.5 are as well, but it all depends on your tastes.
GTA3 is just awesome.
vsp: When I went to Phil's, the Barracks OL was there but no tank. ?