This Columbia Men's Rfid Security Blocking Traveler Wallet is simple and secure.  I like its low-profile retro color and design.  It's soft and comfortable to hold and pocket.

Even though it's named "traveler wallet," it's not deep (tall) enough for certain country's wider bills.  It's perfect for US dollars.

I recommend it, but if you are traveling around the world, just know that some bills might not fit entirely.