New Super Mario Bros. 2: 1-A

We need 5 Star Coins to unlock this level. On the bright side, we get a free save. This is mainly a pipe area. Kick the Koopa shell into the gap to get an item when it bounces off the brick block. Pound the bricks over the one-way arrow door and go down, and you find the first Star Coin over the brick blocks at the bottom. Go right and take the green pipe cannon to the midpoint. For extra coins, go back left and hit an invisible block next to the pipe on the right. This will allow you to hop over the pipe on the left and collect coins on the way down. Walk over to the one-way door to the right and drop down. You'll find two Gold Rings over some Koopas. Activate the first Gold Ring and throw the Koopa shell to the right. Be sure to get the coins coming out of the pipe where the Piranha Plant was. A little farther right is another Koopa and Gold Ring. Send the gold Koopa shell into the stacked Goombas. The brick block under the pipe has the potential to become a Gold Block, so let the Koopa shell hit it. Stand on the pipe directly over the Gold Block to collect the coins that will come out of it. Then pound the brick block above you to turn it into a Gold Block that you can wear. Go right for a pipe cannon up. Go left and kill the giant Piranha Plant, then drop down to where it was to make coins appear above. More coins will appear if you drop down to where the Koopa is. Go back right and kill the Piranhas. Drop down the one-way door and let it close. Then go right for the second Star Coin. Drop down to the ground where you'll find two Piranhas. Go down the pipe, where you'll find a Gold Ring, a Koopa, and some Piranhas. Activate the Gold Ring and kill the Piranhas with the shell to make lots of coins appear from the pipes. Go through the pipe and you'll come out from a pipe stair case. You're near the flag. The third Star Coin is pretty tricky to find. At the top of the staircase, you'll find four pipes floating in the air with Piranhas. Drop down near the one on the left and hit the invisible block under the opening to the pipe to the left of it. Enter that pipe and kill the giant Piranha. (There's a Koopa there, if you need it.) Behind the Piranha is the third Star Coin. Go back through the same pipe, then go to the flag.

Coin Total: 38,876
I didn't play through this level THAT many times. I moved on after trying to find the third Star Coin and came back and found it before I beat the game, and the above total is when I came back. When I gave up, my total was 8871. There are a lot of coins in this level, especially if you start the level with a Gold Block.