When I was dropping off some of the brochures I saw this sign, which struck me as being rather amusing. This is a very Singaporean sign for one thing because the word 'horning' obviously isn't used in this context anywhere else in the world.
Also surely beeping your car horn has to be allowed in some instances - for example, if someone is unaware of the danger of an oncoming car. There were quite a few signs up (no plucking of flowers and no bouncing of balls off the doors being two of them!) :)