Are you talking about Function parameters?
Do you mean predefined lists with fixed values (for example, color names, blend modes etc.)? Or custom lists, where you enter values yourself (for example enemy types)?
I can see how custom lists may be useful in some cases. Say, when you are calling "SpawnEnemy" function, instead of typing "zombie" in function parameter, you can select "zombie" from the drop-down list. However, there is a serious problem - you will lose the ability to enter expressions in this field, for example choose("zombie", "vampire").