cannon game aiming with mouse maybe crosshairs or an arrow to show where it will hit

I want to be able to shoot a cannon controlled by the mouse position that shoots in that direction. The game will be about trial and error to try and hit the target, like a 3d angry birds. I do not want a raycast because it would be nice to face the cannon at the target and have the control feel nicer and smooth. I think having a crosshair object between the target and cannon would be good as the cannon can face it and the cannon wont be shooting directly towards the target.