Even if you don't have Cornish ancestry, Cornish is a good choice to introduce you into the Brythonic branch of Celtic languages (which are often considered a spot easier than the Goidelics!). In addition, you will have a bridge into Cornwalls pre-Anglic history.
Cornish
French
German
German is often considered difficult. Let me just say, it is not. It is logical, mathematical and uniquely (near) exception - free for a natural language. So, learn German, die Sprache vom Logik!
Swedish
Talar du svenska? Nej? Oh!
If you don't speak Swedish yet, you're going to enjoy delving into a cozy Scandi culture of köttbullar (meatballs), kannelbullar (cinnamun buns) and fika (Swedish afternoon coffee). If you know a bit of Swedish already, why not continue?0
French - la langue d'amour (the language of love)! Impress all with your fluency, grammatical accuracy, and comprehension in this feeling language spoken by 220 million.