Athletics - a key part of every Olympic games.
Basketball - well, it's clear USA will take this down, but still the top team sports event...luckily almost all the games are broadcasted.
Football - usually I sort of ignore this during the Olympics, but try to watch at least the semis and the final. Plus seeing Brazil to fail to win the gold at home will be fun.
Swimming - it's usually the main thing going on during the first week of any Summer Olympics...lots of world records etc. although I didn't bother watching it much last time.
Golf - not sure how much of this will be shown, but this is an historic event as it's in the Olympics for the first time since 1904.
Fencing - women's épée, to be precise, as Estonia has a decent shot at medals there.
Weightlifting - some Estonian giant has a shot to medals there, after so many of his competitors have been disqualified due to doping.
Rowing - again, one of the sports where Estonia has a medal chance.
Wrestling - same...won't watch women's wrestling though, which is an abomination.
Badminton - very entertaining to watch, although not shown a lot.
Archery - same
Diving - also a cool one to watch
Volleyball - will try to watch the final at least.
Field Hockey - not shown a lot other than maybe the final.
Handball - cool sport too, might watch a couple of games.