When you're baking something that's difficult to remove from a standard cake pan, like a cheesecake, you'll probably choose a springform pan. But the problem with springforms is that they tend to leak.
For another option, there's the 9-inch square PushPan from Kuhn Rikon ($32.09). It has a loose bottom, much like a tart pan, but the difference is that the removable bottom of the PushPan is rimmed with silicone, creating a gasket-like seal to keep the dessert in the pan and the water bath out. My first thought was, "Why didn't someone think of this before?" It seems obvious now that it exists.
The bottom fits quite snugly. It's suggested that you use a bit of oil or baking spray to help it slide into place, and that oiling really is necessary. Once oiled, the bottom slid into place easily, and it was just as easy to unmold the baked goods. I had no leakage at all during testing.
This pan is a bit expensive, but considering that it can be used in place of a standard baking pan, a springform pan, or a tart pan, the price seems much more reasonable.
One slight disadvantage is that the pan isn't quite as deep as it seems because of the way the bottom piece fits. The depth of the pan measured from the outside is 2 3/4 inches, but the interior depth is 2 1/4 inches—think of it as a 2-inch-deep pan and you're fine.
Besides the square pan I tested, there are round pans in three different sizes.
Disclaimer: Testing samples were provided to Serious Eats.