StarDunk is a free, 2D hoop-shooting game with slick production values, great multiplayer features, and an optional system of in-app purchases that somehow isn't obnoxious.
StarDunk adds fun twists to some pretty basic gameplay: You have two minutes to score as many baskets as possible, as you touch the screen to set your ball's trajectory and then release to shoot. The ball is on the right side of the screen and the basket on the left (left-handers can swap sides), all against a spacey backdrop that matches StarDunk's electro soundtrack. The basket's backboard has four tiles that you can light up to get temporary power-ups--everything from shooting three balls at once to adding score multipliers to widening the basket itself. Its good mix of simple gameplay and complex scoring strategy makes StarDunk fun and addictive, especially in multiplayer matches--and now that StarDunk has a critical mass of fans, you can usually join a 400-player battle-royale "contest" within a minute or two, supported by leaderboards on GameCenter.
The more you play, the more StarPoints you earn, and you can then use StarPoints to purchase background themes or--even more useful--special balls that have different sizes, speeds, and bounciness to them. You can also get more StarPoints through in-game purchases or by downloading additional apps, but thankfully many balls can be unlocked just by playing and earning achievements.
StarDunk has some shortcomings, including a lack of depth and its in-game ad banners (although they're mostly unobtrusive, and can be removed with--you guessed it--StarPoints). Overall, StarDunk excels at its fun, pick-up-and-play premise, and it includes countless nice touches, from a slow-motion zoom on your last shot to a cool spinning globe that shows live, in-match score updates from around the world.