One of my favorite fundraisers ever--my youth group has been doing this for about 8 years and still makes tons doing it, and it's super fun.
It's called "flocking"...someone pays you to flock a friend/family members yard, and in the middle of the night, you sneak out and stick a bunch of those big tacky pink flamingos in their yard with little tags around their neck that say "You've been flocked by the (insert organization name here)! If you would like us to come remove the flamingos, pay by donation, and call (insert head persons number). If not, enjoy their company, and we'll come gather them up in a week!
So you get the donation from the person ordering the "flocking," usually a donation to have them removed, an you can even add in something like, "for an extra donation, find out who flocked you and get them back!" Type of thing. It's perfect if there's a celebration at the household (when my little cousin was born, we flocked their house and added an "it's a boy!" Sign, we've done birthday signs, etc. and it's just a fun little harmless prank. We all got really into it when we did it--dressing up in all black, sneaking around developments, just having fun!