Here's my list of sports:
Aww c'mon, marching band counts doesn't it? 
I wouldn't
quite go as far as to say that it's a fully fledged sport, regardless of the fact that I'm in it. An extremely intensive performing art, I'd say, but depending on this thread's definition of sport, I could see how it might pass as one.

[rant warning]
If you're looking at the physical fitness requirements, it's all cardiovascular, and not even that much. Last year in '07, only a really tiny snippet of our show was slower than ~160 or so (and that was because we were marching half-time for choreography), but even then, it took like 2 or 3 minutes for me to get winded (even though there was a huge percussion break during that time

). Compared to football and soccer, both of which I
used to play, it's nothing.
But then there's baseball, which I also used to play, which is a lot easier than MB, even at its most energy intensive, mostly because all it involves is a bunch of short sprints.
Finally, there's the aesthetic value. Normal sports usually include two teams actively competing with each other. In Marching Band however, it's more of a passive competition, because you never really respond to the other bands' actions. For further comparisons, let's look at this chart.
X denotes a large part of the item, x denotes a small part of the item.
MB | Definite sports
x | X physically demanding
| X active competition
X | X practices
X | X discipline
X | X defined teams/groups
x | X teamwork necessity*
I say teamwork isn't a large part of Marching Band because during the performances, you never really communicate with anyone. You look at the drum major, the field, the form, and listen to other people. Assuming you're correctly tuned and warmed up, you can just stare at that drum major and the form and forget about everything else.
I go as far to say that band is a hybrid between a sport and a performing art at best. PCMB's schedule was pretty hectic last year, and the show was loud and fast. I'd say that's probably one of the closest.
Yet I must say that it is demanding, and unless you're in excellent cardiovascular condition, you'll get tired by the end of the show.
To sum it up, marching band (or at least the PCMB) is over-rated by its members, yet under-rated by bystanders who have no experience with it, and regarding more aspects than this, as well.
[/rant]