I always wanted to be able to get control over the mouse cursor without opening a GUI. This would be especially helpful to hover over the stat bars and effects to show their tool tips. Unfortunately, most GUIs overlap the stat effect icons (if you have various active at once), which makes it sometimes impossible to get any information on some effects.

This would also be very helpful for debugging mods!

A dedicated key binding for mouse cursor control would solve this issue (i.e. hold CTRL by default, which is unused iirc).