Always loved watching Rugby unfortunately its televised very rarely here in the states and consequently I've never fully understood the rules and strategies. But you can tell any sport is a great spectator sport if people like me that don't have a clue how to play it still enjoy watching it.
I love American Football also, but like many fans this year I haven't watched any games. Maybe next year they'll get their act together. Soccer is something I've tried to get into on numerous occasions, I even used to play it, but it just doesn't seem to hold my viewing interest very long. To me it's kinda like a NASCAR race, hours of running around in circles and only minutes of actual drama. Seems like I could watch the last 10 minutes of the game and pretty much see most of the action that mattered (same with NASCAR).
The strangest sport to me is Basketball. I find Professional Basketball to be about as exciting as watching paint dry. Yet, I can't think of a more action packed, on the edge of your seat, thrill ride than College Basketball. If you've never had the opportunity take some time to attend a sweet sixteen College Basketball game, do so, it's life changing.
For me - College B'Ball is to sports, what Gibson Thunderbirds are to Fender Jazz basses.