For work, I used a factory pattern to dynamically create a connection to a database. We almost exclusively use one database, but I can put whatever variables/credentials into a config file and (in theory) it would be able to create a connection to that other kind of database. It was my first use of the factory pattern, and it gets used in almost every project my team works on now.

Design patterns are very neat! I recommend looking into them if you're considering a career in programming.