I always found getting outrageously drunk on fine scotch and trolling the shit out of someone, IRL or online, works for me.
On the topic of doing something difficult and fun, I've been looking at fencing classes. There is a fencing studio literally five minutes walk away, with 4 weekly sessions. I'll admit my preferences in swordplay run more towards the ARMA "bash them in the face with your pommel, kick them in the balls and stab them while they're crying on the ground" method, but a more...refined approach could be interesting.
If you're going to carry a sword, it's prolly best to have the whole Assassin's Creed repertoire down