But you shouldn't.
Horns are for alerting someone to something wrong. Something very wrong. Like the guy who posted here about his brakes going out.
They are not for:
Getting mad at a pedestrian crossing the road.
Because someone took an extra 5 seconds to go through a light.
Because someone did something you didn't like.
To say hi to your friends.
Because you're otherwise impatient.
CALM THE FUCK DOWN.