There are a few ways you can leverage this great little cantrip to have some serious fun during your next D&D session. The first way is as a spell interrupt. In the instance that one of your players casts a spell that requires either line of sight or has a long casting time, use minor illusion to bewilder them and make them miss their opportunity. A great example would be if they were relying on enemies being blinded by darkness or fog to sneak up on them for a melee attack – use the concussive blast from thunder wave instead!
Minor illusion also works well as an area-of-effect ability, where you can create multiple copies of yourself and confuse opponents before retreating back into the shadows with invisibility before reappearing later for another attack. Remember, the range of this ability is only 60 feet, which even in D&D 5E can be pretty limiting unless you are using a ritual or item to increase your range.