I like the Adrian Klis wallets. They are incredibly well made, and you can often find them being sold in the +15 downtown. They are leather, and a few of the options are quite slim. But if slim is one of your first criteria, you probably don't want a leather wallet. I'm on my second one, and my previous one lasted about five times longer than cheapo wallets I used to buy. In fact, it is still quite functional, but the edges look a little more worn than I prefer. So, I have a new one.
http://www.canadaleathers.com/wallets.html