Technically? English. Constantly learning here! Had French, German, Latin and ancient Greek in high school but I got rid of three of those as soon as I could. What I dislike about learning languages is that you have to keep up with it so much. Unless you're immersed in the language, you have to constantly work on the language to even maintain a similar level. I've had three years of French and while I enjoy knowing a bit of French and having a feeling for the language, I have forgotten so many words and I'm glad I didn't spend another three years learning words only to forget them.
I took Latin this year and regret it immensely. I've wasted a lot of time learning the specifics of a dead language. I'll be taking Spanish next year, which I'll be able to apply in my life because I live in the US Midwest. Any recommendations for immersion?
I was writing a longer comment but lost it due to losing wifi signal and subsequently restarting Chrome. Anyway, the gist of it: Of those languages, I found Latin to be the most valuable to my linguistic insight. Nearly all West-European languages have their roots in it, including English. I didn't like having Latin because it was a language, not because it was Latin. I mean, I have translated parts of Caesar's De Bello Gallico and Pliny the Younger's letters to his uncle, explaining the Pompeii eruption. Closer to classical history you cannot get. For immersion, I would recommend finding a forum or site on a topic you're interested in, in the language that you want to learn. You could also try reading the Spanish news.