i have 9 dollars and an appstore full of apps that can be bought you can name nine 99 cent games or one 9 dollar game whatever you think has the best value
Tiny Wings - 0.99 Fruit Ninja - 0.99 NBA Jam - 0.99 (on sale, grab it NOW) Battleheart - 2.99 Plants vs Zombies - 2.99 EDIT: Spend another dollar, get First Touch Soccer without hesitation
Plants vs. Zombies - 2.99 - Best Tower Defense game on the appstore Radiant - $0.99 - Best retro Space-shooter Doodle Jump - $0.99 - Endless replay value Call of Duty: Zombies - $4.99 - Best Survival FPS, great replay value
Order and Chaos is really good if you like WoW-esque MMOs, though it does require a subscription after a while.