I remember my ex wife one time trying to chase them away, and when she turned around one of the monkeys ran up behind her and slapped her on the leg.
To try get rid of them we once bought chilli powder and poured it into hollowed out bananas. We then threw them outside and watched as the monkeys downed them. It was then so funny to see them wiping their tongues frantically with their hands trying to cool their tongues down.
We had also heard that monkeys have a instinctual fear of lions, and that if you spread some lion manure around the garden then they wouldn't come near. There is a zoo close by, so we went there and managed to convince the workers there to give us some lion crap (dang it smelled bad!!!!!). We put it in a bucket with some water to dilute it, and then distributed it around the garden. Did it keep the monkeys away i hear you asking. NO!! It didn't...and the garden stank for a week after
I then bought a paintball gun and some plastic balls. When they came close i would try shoot them with that. My aim was terrible and i never actually hit one, but it kept them away for a while