To generalize this: You can cancel any spell with a non-zero cast point (Most spells not based on Hex, Fan of Knives, or Bladestorm, on heroes with a non-zero cast point, note, some spells don't use the heroes cast point
) by issuing the stop / hold order before the cast point. Visual indications of the spell occur normally up until the canceling order is sent ("swirls" being shown on Furion's tp, for example), and no Mana/CD is spent/started unless the cast-point is reached.
For example, without getting into the strategy of it, Sven can "fake" stuns (flashy storm bolt wind-up effects and all) at 0 mana / CD cost to himself to intimidate opponents.
Of course, heroes with 0.00 cast points (shown as 0.00 / X.YZ on the hero page, excepting spells that ignore cast point), or with spells with zero cast points can't cancel before the cast point, as it occurs instantaneously.