Hi! FlyerTalk virgin here with his first post, so please be gentle.
Check out Pelican cases (Google them--they have a great web site). They're relatively lightweight, watertight, come in a WIDE range of sizes and shapes, and are tough as hell. Many of the cases also have a pressure-equalizing valve built-in. Best of all, they cost about 80% LESS than Zero Haliburton cases. Pelican cases are often used by film/video/photography pros, EMTs, SCUBA divers, the military, etc. They aren't very pretty, but I dare any baggage handler to break one! Well, break one without really, really trying. ;-D
I'm Mr. Carryon, but just purchased a Pelican case (18"x14"x7" exterior) so my wife, her sister, and I can check our liquids and gels on our Euro flights next month. Weighs about 6.5 lb and it's built like a brick outhouse. B&H Photo-Video in NYC has great prices on them. (I have no financial or personal interest in either Pelican Cases or B&H.) Good luck!