The laws of physics suggest anything with straight walls and a perfectly flat bottom will be difficult to tip over. When I start hatching babies and need a bunch more bowls I will use PVC with deli cups. I think I'd keep much cleaner water bowls if I didn't have to stack and carry them all to the sink and wash them all tediously every time I want to give new water. Deli cup swap -> done. Throw some in the dish washer if I want to reduce waste.
I'd hate for one of these heavy ceramic bowls to slip out of my hand and crush a baby...
For now I use this:
http://www.amazon.com/Ethical-5-Inch...+pet+bowl+5%22
...but that is by no means the most cost effective way to get a decent bowl.