One Note. My short term memory is appalling (neuro issue), so I have running lists on there for everything. General things to do, a daily to do list that I tick off & copy over to the next day. Birthday present ideas / things I've already purchased.
Period tracker. I'm fairly regular & get migraines at regular points through the month, so it helps me predict those too.
Online banking. So much easier!
Online grocery shopping - no car, disabled, live semi-rural with not great public transport. Again, much easier. Morrisons very reliable IME, only had 2 subs in 3 years.
I have a torch app but rarely use it. It eats the battery! Good though.
Citymapper - great for London. I wish the developers would realise there are other cities though... I occasionally try it out, in the forlorn hope it might work. No. Google Maps just doesn't compare.
Galls me to say it, but Amazon. I do try to shop in RL or with smaller online stores before resorting to them, though.