re: looking for good ideas to prank my neighbors

If you want to rub something on his door handle, don't put shite or gum on it, put some terrible cologne or maybe something really strong like garlic or cheese on it. Just make sure you repeat it on multiple days. You don't want him to immediately go "dammit I'm going to get that SOB back". You want him and everyone he knows to wonder why he smells like $3 cologne all the time.