Instead of telling you specific languages I'll suggest some language types: object oriented, functional and procedural. Specific languages depend on the software you write, the language of choice of the team you may be working with, operating system, etc. Just pick something from each of those types and you should be fairly well rounded. Never be satisfied with what you currently know and keep learning new stuff.
Since you'll likely be working with bucket loads of data as an actuary, there's a high chance that you'll need to know some SQL. Other than that it's hard to say because, as stated above, it's very environment-dependent.