First of all, they have a mustache. Both the males and the females have them, typically a long, white handlebar type. Second, they have excellent aim and precision in flight. Here's where it gets WTF: while they normally use this skill to dive into the water for little fishes, sometimes they use it to steal food. From SEA LIONS. Out of their MOUTHS. Unfortunately I can't find any photographic evidence of this hard core behavior, but you can bet if I ever go to Peru I'm staking them out until I get a picture.
They also meow like cats. So, we have this little bird with a 'stache flying into sea lion mouths to steal fish, while meowing.
Other items of note regarding the Inca tern: the length and condition of the mustache and the coloring of its yellow wattles indicate health to potential mates. They like to nest in rocky cliffs and not on the beach like some other terns; I like to think that this is because they are more bad-ass than other terns. They are the only member of the genus Larosterna in the family Sternidae. Again, I attribute this to their high level of awesomeness and think they used up all the awesome so there was none left for there to be another bird in the genus. Juveniles don't have the rockin' 'stache or the brilliant leg and beak coloration, but are more of a brown in these areas. It takes time to get that awesome!
If you're ever at the National Aviary in Pittsburgh, you can actually feed these guys. They swoop down and take a little fish from your hand. One will spot your sardine from all the way across the habitat and ZIP! The fish is gone. If you aren't paying attention, you just feel the air moving and the fish just disappears. Definitely worth the trip to PA if you aren't going there anyways. My trip there is the source of much of the info I know about them, but you can also read about them here, here, here, or here.