Relevant Ways to Challenge Oneself (Undergrad)

I'm a freshman in college; however, I'm in a bit of an awkward position as even with a double major (Finance and Economics) I'm able to graduate within three years. My school offers an opportunity to take masters coursework as an undergraduate, graduate undergrad, take a year of grad classes, and then finish with a masters degree. I've decided to pursue this path (Masters in Business Analytics) because I'm interested in pushing myself academically and would like to stay here and grow for four complete years.

While all these opportunities are awesome, I am interested in exploring other ways I can challenge myself. I'm planning to pursue a career in IB after college, so I'm specifically looking for endeavors that could be relevant to my career. My current list includes studying for the CFA Level 1 exam and/or conducting independent economics research. I've also considered adding more math on top of the stat used in econometrics and time-series econometrics, but I'm not interested in becoming a quant and do not want to waste my time (thoughts?). On the fun side, I've joined a fraternity, added a Spanish minor, and am planning to study abroad this summer.

It's hard to reconcile my position ahead even with the early recruiting process of IB. I've joined the finance societies, networked, studied, and networked more. Now, I'm about ready to compete for Summer Analyst positions, but I'm a year younger than what most firms are looking for. I just feel I've hit a ceiling here as an underclassman and the last thing I want to do is sit with my feet up for these next few years.

My question to those working in IB is: Outside of your major, what did you explore in college that you've found helpful in your career? The more surprising, fun, or seemingly random the better.

Thanks ahead of time for the advice!