I'm a leftie too. Like bluenomi I have always used the computer mouse with my right hand, makes it easier as I often write while on the computer do my left hand is free to write. I've only recently had to switch to a special left handed mouse but that is really due to my arm injury.
I hate pens with gel ink because my hand travels over my writing and smudges it. All the lefties I know have terrible handwriting but I actually get lots of comments about how neat mine is. I have been pedantic about neatness since primary school though
my teachers told me off for taking too much time making my work neat!
I struggle with normal scissors and had to buy left handed ones for work a few years ago. My thumb gets squashed in them and gets painful so left handed scissors are great for me.
I second the comment about small space bars on keyboards, I use my left thumb to space too so prefer longer ones. It's not a big issue though. When I was still allowed to type before I got my injury I was an excellent typist (if I do say so myself). I had to type info as clients gave it to me over the phone and they always commented that they could hear me typing and had never heard anyone type so fast
so it's not a real hindrance when it comes to keyboards/mice IMO.
I don't know if it's a common leftie thing, but I tend to do nearly everything left handed. Carrying things, opening doors, stirring etc when cooking, everything. My teachers thought that contributed to my clumsiness as a kid but it's most definitely a family trait so I personally don't believe people that say lefties are clumsier!
I find most notebooks annoy me as when I start writing on a new line my hand sits on the binding and is uncomfortable. I tend to buy lots of different notebooks to find a comfy one and DH who is right handed gets the others!