Viewfinders/telescopic sights with the left eye.
Ah yes - I'm left eyed and right-handed. Which means I'm inherently bad with guns.
Fortunately this hasn't really been a problem.
A gun range safety officer told me to ignore any issues like that - if I wanted to become truly efficient, I should learn to shoot with both eyes and both hands. "What happens when you're hiding around the wrong-handed corner?" he said. Not really a problem for someone who only went shooting a couple of times.
As for the rest,
Lefty - writing, Frisbee, small hammer, hand axe, carving and craft tools, snooker / pool, football
Righty - hitting things with sticks / bats / racquets, throwing, guitar, mouse, eating irons, big hammer / pickaxe / axe, martial arts weapons*
I can never tell until I actually try something whether I'll be left or right handed at it, but generally it seems to be fine motor control on the left and power on the right.
*Which of course are practised both sides even when they're not, such as Japanese sword arts.