Obviously, some people watch these sports, but compared to the big dogs like gymnastics and swimming, their viewership is lacking. Here's a list of sports that aren't nearly as popular, but could be.
Equestrian

This may sound crazy, but isn't the horse doing all the work here?
Why You Should Watch It:
This sport is actually pretty cool because it's the only one that involves a person literally imposing their will on an animal, while the human gets to sit back and relax, sort of. And those of you that have ridden a horse know that it's pretty tough on your legs and back, so it gets some more points there.
Why You Shouldn't Watch It:
It's tough to explain to your buddies why you're watching horseback riding. Unless they're horses on Deadwood, they won't get it.
Badminton

Wait, the sport you signed up for in high school gym because you knew you could easily sneak away to smoke pot is in the Olympics? Like, the Olympics Olympics?
Why You Should Watch It:
Because it's people playing Badminton professionally! It's like professional hackey sack; you always thought it was a joke-game, and then you see these guys rockin' it on the court. And these guys are good. Chinese Badminton bad ass Fu Haifeng once served a shuttlecock at 206 mph. Almost NASCAR speed, son.
Why You Shouldn't Watch It:
Your lame ass roommate won't stop saying "Look at him hit the shuttlecock" and "I'd let her play with my shuttlecock" and "I wouldn't let Fu Haifeng near my penis."
Team Handball

Either this is team handball, or he's a super pissed soccer player.
Why You Should Watch It:
It's like a combination of ice hockey, water polo, dodgeball, soccer, and basketball. It basically covers almost everyone's favorite sports, and is super high scoring. It's not popular at all here in the US, and it even took until this year to actually get a team. Another fun thing to do is get super into the game, so that if it ever becomes popular in the US, you can become ESPN's correspondent on everything handball. Or just use it to gamble.
Why You Shouldn't Watch It:
It's like coming in halfway through a season of Lost; you'll have no idea what's going on, and it'll be over before you ever catch up.
Field Hockey

They're actually chasing down a squirrel that hopped onto the field.
Why You Should Watch It:
It's actually pretty bad ass. It moves fast, there's a lot of action, and the players are really skilled.
Why You Shouldn't Watch It:
Despite the speed of the game, there are a lot of rules that prevent the game from being faster and from having more action. These rules limit amounts of body checking and use of the stick, which in America, are generally regarded as important plot points for our favorite sports.
Fencing

I'm stabbing you! Should we grab coffee after this or...?
Why You Should Watch It:
It's people sword-fighting! It's as close we'll come in this "civilized" world to watching old-timey 1700s dudes go at it with swords. In 1924, members from the Italian and the Hungarian teams decided that a scoring discrepancy meant that the best fencer had yet to be determined, so they got to dueling in order to find the real winner. Here's to hoping pride rules this year's games, and we can witness an unsanctioned, street rules, death match.
Why You Shouldn't Watch It:
Sadists will be dissapointed to see that participants wear protective gear all over their bodies to prevent any sword related injuries. The squeamish wouldn't like to know about the possibilties of gruesome deaths, like that of Dr. C.C. Terry. He was killed when the tip of his opponents foil broke off and entered his right eye, and then his brain. He died soon afterwards. So what if it happened in 1892?
Table Tennis

Some games can go on for years. This lady started playing in 1924, and refused to stop until it became an Olympic sport in 1988.
Why You Should Watch It:
Table tennis is a pretty lofty term for ping-pong, isn't it? It's another sport you can add to the "This game I play when I'm drunk is an Olympic sport?" list. But similar to the Badminton folks from above, the people who play this sport professionally are insanely good. They have to be, because according to the IOC website, ping pong is played competitively by 40 million people worldwide, and by countless people hanging in their friends basements while drunk/high on a variety of substances. With that in mind, it should be good to watch the pro's hit the ball over 80 mph. You know that scene in Forrest Gump when he's hitting the ball super hard, and it's flying everywhere? That actually happens in the Olympics. Without as much Tom Hanks, though.
Why You Shouldn't Watch It:
It's a total mindfuck watching a bunch of people swinging their arms at full speed, at a ball you can barely see on TV, only to find that there actually IS a ball on the table.
Shooting

The psychiatrist said this would be therapeutic for me.
Why You Should Watch It:
Similar to fencing, this sport is dudes shooting guns. It's probably the only sport in the entire Olympics that YOU could be good at, given the time it takes to practice shooting. But luckily for you, it doesn't require any "running" or "being in shape like the runners" that's been holding you back from real competition. Just ask Oscar Swahn, he was 60 years old when he won his gold medal, and rest assured, he wouldn't have placed if there had been any physical requirements. No sir, this sport is all mental focus and mind-over-matter style nerves.
Why You Shouldn't Watch It:
You'll start to be like "Nice shot...I can do that...Man I hate that co-worker...what a jerk...the office is much smaller than the Olympic range...I could take three or four of those assholes out before anyone knew what was going on...then three or four more when everyone started running...I'm going to Wal-Mart..."