To view the best players screen (which is firstly seen on completion of the game), press B + Start at the title screen.

Press Forward, Forward, Forward, B

Hold B, press Forward, Backward, Forward, and then release B

Hold B, rotate the D-Pad clockwise, and release B

With any sword equipped, 360 motion on the d-pad, forward, back, forward, B, pause for half second, B

At the Diary (save select) screen, press B + Start to access the game's sound test screen.

360 motion on the d-pad, forward, back, forward, B, B, B (can also be ended after the 1st or 2nd flip)