Darts are a fun game at it's own and they are great for parties as well, but, if you really want to use them in an actual party game, then Darts Challenges is the game for you.
Before the party, mark the fields on the dartboard with special challenges. You can either cut out papers in the shape of the dartboard fields and write challenges on them, or you can take the easy way and use a legend type board. The second way is way easier. All you have to do is write what field is what challenge(for example, 9 Rad = run naked down the street and back).
When you are done with preparations, start the game. Each person at the party gets one shot and whatever they hit, the have to do. It's as simple as that!
You can also play in pairs and see who gives up first.
You can also turn it into a drinking game, or partly into a drinking game. Each field on the dartboard marks a number or kind of drinks a person has to drink. Alternatively, you can set a "drink price" for each challenge and the person who hits it can either drink or do the challenge.