How to introduce "Husband" in social occasions? Some common words are 先生 or 老公,

Are there any other options that would be more socially appropriate?
老公 is more for casual conversation. e.g. 這是我老公 

先生 can be used in a more formal situation. e.g. 這是我先生 

In a even more formal situation, you can use 外子.  e.g. 這是外子