I'm left-handed and so is my brother, both parents right-handed. Grandfather was 'ambidextrous' but was actually a leftie who was forced to use his right hand.
I am very left-handed and was always surprised how well my brother adapted to the right-handed world. He will happily use right-handed scissors in his right hand. I had left-handed ones from an early age. I am older so he could have used them but chose not to.
The only thing I do right-handed is hold my knife and fork 'correctly', while my brother eats left-handed. The disadvantage of this for me is that I cannot manage to carve a joint of meat nicely - because I don't have the dexterity in my right hand but it feels wrong to hold the carving knife and fork the other way round.
Took me years to learn to tie shoe laces.
All my kitchen knives are double sided.
Mouse is on left hand side of computer. I turn the page almost at right angle for writing and am always on the lookout for non-spiral-bound notebooks.
I always thought we read magazines backwards because we flick backwards using our left hands instead of forwards using our right.
I'd forgotten about the chairs in lecture halls - used to drive me crazy when I was a student!
I didn't even realise about door handles! There is actually one left-handed one in our house because of the way the door opens.
I am musical and play woodwind the normal way round (no choice really because of the way the keys are positioned, though the recorder could technically be played either way). Lots of right-handed children actually have trouble starting wind instruments because the left hand goes at the top. I play guitar left-handed (strung 'upside down') and learned mirror image. I don't think I could play an orchestral stringed instrument as it would just feel too backwards.
I loathe automatic gates - lived in London when they first came in and I didn't realise for ages why I found them such a pain! I cannot do it right-handed so always had to hold the ticket across my body to get through - lots of clumsy juggling which is tricky when the tube is busy.
Banisters are almost always on the right! Kitchen sinks can be either way round depending on your kitchen layout but I agree one that has the drainer on the wrong side is a pain.