Super Mario Bros.:The Lost Levels have been recovered a second time. That is to say, the game has released on 3DS via Virtual Console, and is priced at about $6.50. Currently, only a UK release is noted, but those of you in North America should check, too.
If you're not familiar with Lost Levels, it's what some consider the "real" Super Mario Bros. 2. Originally released only in Japan, it was since remade and released on SNES outside the region, and also released on the Wii Virtual Console. Like the previous VC release, this 3DS version is the original, without the fancy 16-bit graphics.
Lost Levels is quite possibly the most difficult Mario game you'll ever play. In fact, this is the reason it was never released outside of Japan originally.