Long-legged fly family Dolichopidida possibly Condylostylus sp. EDITED TO ADD: lets call it Condylostylus patibulatus, a species common to the northeast, which I have had identified elsewhere from my yard.
I kind of hate myself for using this as one of my 100 species. Why? Because I can really only identify it to family. Stay with me for a minute. Long-legged flies comprise a family (called "Dolichopodidae") of small predatory flies. There are something like 7000 species worldwide, 1300 in North America. In other words, if I were a very skilled and diligent fly identifier, I could do a decade or more of 100 more species projects with just long-legged flies. There are more species of long-legged flies than there are species of mammals.
I have a strong feeling that this long-legged fly is in the genus Condylostylus, based more on comparing my photo with the bugguide.net photos than anything else. These flies, and most flies by the way, are identified primarily through looking at the veins on their wings. Most of the long-legged flies I've seen have been about the size of fruit flies, so examining wing veins is something you do after your specimen is dead and the wing is detached and under powerful magnification.
When I learned what long-legged flies were--active predatory animals--I was amazed. If you spend an hour in a garden or among the tall weeds, you will see hundreds of them. That means that there are thousands of smaller prey animals, most of them so tiny that they are beneath your notice, that these flies are catching and killing. How wonderful would it be to be able to see things from their perspective for a short time, to watch these metallic monsters (which are armed with the most advanced flight ability that evolution has produced) chasing or ambushing other insects and draining them with their piercing mouthparts. Forgive me, but it would be like Star Wars crossed with Dracula.
So I'll leave the other 1299 species alone for this project, and let this under-identified specimen stand in for the entire family.
EDITED TO ADD: I would be remiss if I didn't quote bugguide.net's note on long-legged fly behavior: "Adults mate after elaborate and unique behavior, involving the males displaying their legs to the female."