That you can actually use the spinning to suck items to you? I've just discovered this apparently and spinning creates a sort of vortex that draws in nearby items. Useful when you're trying to move quickly or going after a falling item. This is probably done best with using the r key to spin.
I didn't know what thread would be good to mention this in, so I decided to make a new one. Although I'm sure others have discovered this, but not everybody.
Anyways, to make this thread an useful one and not spam, people can post interesting facts or strange things that you have noticed, or even different ways of doing something (I'm not talking about boss battles here, although some minibosses are ok, such as the Sea Dragon)