The Dart
Perhaps the world's most common paper airplane, the Dart is worth a closer look.
It's a good test platform for variations, and an enhanced version is shown as well.
This remarkable design is also very common. It's a medium glide sport plane that holds together at the bottom of the fuselage just by the folding. There may be a name for it already, but I don't know of any, and I'm calling it the "W-1".