Tank Top Glitch
When a tank slides on a single force floor or ice corner, turning direction from horizontal to vertical or vertical to horizontal, and hits a blue button as a result, the blue button will take effect before the tank is discovered to be moving in a different direction, and the switch will take effect against the original direction of the tank, rather than the new direction. The result of this is that the tank spins like a top, giving the glitch its name.
If the tank slides for two tiles or more, the glitch will not be triggered, and the tank will rotate 180° as it would under ordinary circumstances, effectively turning back onto the slide.
The glitch was originally discovered by David Stolp, and described to Mike Lask, who made a level based off the use of this glitch, called Tank Bug. This is level 320 in MikeLrejects.dat, and an AVI solution below, yielding the current 124 bold time, demonstrates how the glitch and the level itself works. The glitch also appears in a few other custom levels, but in no official levels.