Cantonese (or Mandarin) so that I will be able to talk to people from the next world superpower.
For me it would be Spanish, so I could talk with all the workers on construction sites.
Korean, would be awesome :) watching korean dramas and stuff like running man with subs would be nice
I think Google translate man
Japanese, just so I don't have to put the work in. I'm currently working on learning Spanish, Japanese, and Korean.