The best ones are the ones you make yourself. Learning theory and brain research indicates that when you write something down it consolidates the information more than if you only read it, only hear it, or read and hear it. Yes indeedy, this does take some time.
You will doubtless get posts from people who have bought this deck or that, with reviews of how much they like them. Fine. In a few months we'll be hearing from those people who can't seem to remember anything.
When I was an instructor I did not accept bought, preprinted med cards. I wanted to see that the information had been given a fighting chance of actually being retained, not just pulled out of a stack.
I know I'm probably hopelessly old-fashioned about this, but you know what? There are no shortcuts to learning. Buying a set of cards is fast, not that expensive, and makes you think that you've done something, but you really haven't. Get a clue: blank cards from the stationery department and a good set of colored pens are cheaper, and will make you learn better even though it takes more time. Because it makes you take more time.
How much do you really want to learn this stuff? Put the time in to do it right. You can't really short-cut learning.