Temporarily Disabling car

I want to temporarily disable my Aveo to keep someone from driving it. They have a key and we share the car, but they take the car whenever they feel. What are some good way to quickly and easily disable a car, or keep it from starting, other than messing around with the battery?

flatten the tires, its a lil extreme, isnt there a fuse you can pull like on the positive battery cable. i think there is one on mine. pull that out whenever your done with the car. i know you said you didnt want to mess with the battery but its about the only other thing i can think of.

Remove the fuel pump relay

wheres that at?

Don't know,probably in power distribution box(fuse/relay box),check the owners manual.
I'd have to look it up,what year and model?