Free (iOS, Android) By Visio Objects
We have seen all types of calculators. But this one is way different. So different that you can scribble any equation or problem on this app and it will do the calculations for you. Yes, it does get a bit confused if your 3 looks a bit like 5 and if you but a / instead of the divide symbol. But ask it to do a very complex equation with a couple of square roots and it won’t have any problem giving you the solution in a jiffy. Recommended for adults and school going kids alike.