I'm a big fan of ten dollar quickies and The Last Guy is one of my favorites. It's a total anachronism -- an eight-bit-inspired game with all the power of a modern console.
You must save the humans from the zombies. You run around collecting people from their hiding places, and they follow you to rescue zones. The more you find, the longer they line up behind you ... and the more likely a zombie will spot them as you run past.
These are the sort of gameplay rules you'd give to a Z80 processor, so the PS3's Cell processor just shrugs them off. It leaves plenty of processor time for decorations. There’s a super-catchy soundtrack played on a Moog synth. There's the playing board itself ... each level is based on a satellite photo of a real city, loviningly traced and colored into a beautiful 32-bit image. The humans scream and shriek when zombies get close. And there's a smooth Japanese announcer guy.
It's a ton of small details crafted into a coherent whole that make the game totally compelling and addictive.