1. Tic Tac Toe
Are you on a long airplane trip. Need a quick game?
Tic Tac Toe grid from Optometry Student website
Of course there are more complex Cartesian grid games such as checkers and chess.
If you need to quickly display data, then this is the old-school way to do it. Plot the points and connect the dots.
Graph from Green-Planet-Solar-Energy
Just think about it. How long would it take to tile your floors if you could not just do this (see pic).
Graph from Wikipedia
A form of rasterisation, mosaics can be used to represent pictures of people, objects and places.
Mosaic of Bob Marley from Art-Heist
Digital cameras also use rasterisation to take quick pictures of events, vacation and family gatherings. Leonardo da Vinci would argue that there are better ways of painting pictures.
Cartesian grids can be used to quickly obtain aerodynamics results for 2-D and 3-D problems if you can solve the boundary problems (without using cut-cells).
Thanks for reading.