Make a backboard out of plywood and attach inflated balloons with push pins. Many suppliers have 4" to 5" balloons specifically made for this game, along with wooden or plastic darts. Each player gets to throw three darts at the balloons. You can award prizes based on the number of balloons popped, or attach a tag to each balloon that states the prize won. This game requires alert operators, don't let kids run this game!
If you don't want to use metal-tip darts, consider a Velcro dart or lawn dart game. Also see the Reverse Dart Game below.
Shooting Stars: Use balloons printed with stars.
Poster Darts: Use small inexpensive posters as the targets. Player wins a poster like the one they hit.
Card Shark Darts: Use oversized playing cards as the targets. You can decide what the winning throws are; examples would be two of the same suit, two matching numbers or face cards, or make it into blackjack and try to beat the next player's "hand" by getting closest to 21 without going over.
Go Fish Darts: Use a deck of "Go Fish" playing cards as the targets. Player wins by hitting matching cards with their darts.