One item, in regular-sized containers, that always leaks when packed in a suitcase is aerosol hairspray. Avoid the problem by buying a small purse-size container and include it in your 3-1-1 plastic bag when you go through security. The Transportation Security Administration allows small aerosol cans if they are for your personal use.
If you prefer the non-aerosol, pump-spray type of hairspray, consider transferring the liquid to a leak-proof liquid medicine bottle. Rinse out the pump-spray apparatus and pack it in a separate plastic bag. When you reach your destination, simply pour the hairspray back in the pump-spray container.