Well, that's an easy one for me. Football/Soccer, without any second of hesitation. Despite that I play it about two times a year, I am still a proud supporter of SC Heerenveen, and follow it at any possible time.
I'm not too good in the sport myself, partly because I had no interest in it for quite a long time. It came a bit late for me, and I was too old to actually do anything with it. Nowadays, I play it about two times a year together with a few other friends. Imagine this: About six people who got an office-job try to play football/soccer together. We take an entire day to play it, but every ten minutes we take a break of about half an hour.
Of those friends, I'm the only one who supporters a team though.
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the logo of S(port) C(lub) Heerenveen</div>
Besides that, I don't have any particular interest in any other sport. I hear a thing or two about hand-ball, tennis and hockey once in a while, but I hold no real interest to it. If I had to pick one out of those three, I'd probably go for tennis, but all in all, I suck in pretty much all four of them, so...