As you might realise, this idea is a spin off from the well-known punkin' chunkin' competition. It's a great fundraiser to launch in the fall at the height of the pumpkin and gourd growing time of the year.
You have the option to either allow teams to construct their own catapults or trebuchets, or to build a single one to do all of the flinging required. One way to raise funds is to get each team to pay an entry fee; alternatively you can get people sponsoring one of the pumpkins or gourds to be flung. Award prizes to the teams that are able to throw their pumpkins the farthest. You might want to have a second prize for accuracy too.
Set up a pumpkin target shoot, where teams fire mini gourds at cardboard standees and attempt to knock them over. A long open space is required for this part of the event — a football field, an abandoned air strip or an unused farm field would be ideal.
Have a concession stand available offering visitors hot mulled cider, corn dogs and maybe a corn roast as well. You could also introduce a bake sale around the same theme, offering items such as pumpkin pies, muffins, and cookies. Make sure everyone knows that none of the pumpkins will be wasted, as the leftovers can be covered by a future bake sale.
You might want to take advantage of Halloween by selling pumpkins that can then be carved into jack-o-lanterns. Alternatively you can hold the event after Halloween to give people an opportunity to get rid of their used pumpkins.
