Apologies for the poor pictures, but here's a little bee-mimicking robber fly, after and before catching a tiny bee for dinner. I followed this wily hunter around for quite a while, and he wasn't pleased with my interference so he didn't let me get very close.
Time to continue with more flies! This guy is from genus Cerdistus, part of a group of successful aerial predators known as robber flies. Harmless to humans, they catch other insects on the wing.
If you're interested in how I can tell it's a guy and not a gal, here's a gal! At the tip of the abdomen, males have grasping appendages and females have poking ones: it's an ovipositor for laying eggs, not a stinger.