Doing - endurance. I've done SJ, eventing and dressage over the years but endurance presses all the right buttons. However, it's not really a spectator sport so I love watching eventing.
Show jumping - it was this discipline that captured my imagination when I was very young. I'm also interested in eventing and top-class dressage. Eventing is not the ideal spectator sport in my view, because it is not normally possible to watch all of a competitor's cross-country round.