er..
i've gotta say it's a tie.
between tons of things.
When I learned to solve a:
2x2x2 Rubiks Cube
3x3x2 Rubiks Cube
3x3x3 Rubiks Cube
4x4x4 Rubiks Cube
5x5x5 Rubiks Cube
6x6x6 Rubiks Cube
7x7x7 Rubiks Cube
etc etc etc
11x11x11 Rubiks Cube
Pyraminx
3x3 Mirror Cube
yeah..
i'm a nerd