I think a party favor should be just a small token to your guest to show appreciation for their attendance at an event. Is it necessary? Absolutely not. With that said, I do believe it's a nice gesture. After all, your guests took the time out of their schedules and in some cases, brought a gift.
It's true party favors have probably gotten out of hand but here's a small token that can be tailored to suit almost any party theme:











