Parties where giveaways are common, say, a birthday, are a great venue for those who want to distribute promotional materials to reach target buyers.
For example, sachets of Skeeter Guard patches can be included in the loot bags (sans the leaflet, of course). The promotion wouldn't be too in-your-face and the parents are likely to use it because it was included in something given away by someone they knew and trusted.
It goes without saying, of course, that hosts should only include stuff they believe in with the loot bags, so this advertising option isn't really open for everyone. Still, this is a great gimmick to dispose of those sachets and packets your company spends on that will really reeach your intended market.