A brown, leather, noname bi-fold. My dad gave it to me when he got a new one and it has served both of us admirably, its still in great shape except for a stray string or two. Been underwater a few times too, just takes a few days to get its sheen back.
I work at a toy store and like any retail worker I see plenty of wallets day in and day out, and the people who own them. In my boredom, I've developed a theory: fathers with thick wallets are pushovers. It seems everytime I see a comically overstuffed wallet its owned by a guy whos a big softie and lets his kids walk all over him. You should see some of these wallets too, some of them are literally bursting at the seams. One guy had a bi-fold wallet that was so large, both halves had twisted in opposite directions to accomodate the bulk. Huge pushover.
My own wallet is maybe 1/2" thick, which is just bordering on too much for me. My dad's is quite slim indeed, and his personality fits nicely with my theory. So, how thick is your wallet?