Nice in theory. But the reality is that either Trump or Clinton is going to be president. The closest thing to a viable 3rd-party I've seen in my lifetime (and I was a kid at the time) was Perot in the early '90s. He had much better numbers than either Johnson or Stein and even he got soundly trounced.
And Johnson and Stein have their own issues. Johnson is woefully ignorant on foreign affairs, to the point that I have to believe that it's willful. He just plays it off in an "aw shucks" manner as opposed to Trump's overt cluelessness. And Stein is an economically ignorant, anti-science, anti-vaxxer loon.
If the Republicans hadn't presented a candidate that's just so bloody overwhelmingly and irredeemably awful... like if they'd nominated Kasich, Graham, Pataki, or even Jeb; I might have been inclined to just leave that part of my ballot blank and say "a pox on all your houses". But they didn't. They didn't just offer up one of the unreasonable and terrible candidates from their lineup. They chose absolutely the worst one out of the whole lot.
So I'm voting strategically. I may not like the 2-party system. Hell, I think there'd be a lot to be said for scrapping the whole thing in favor of a Westminster-style parliamentary system where minor parties can cooperate and have a reasonable shot at shuffling the majors aside and forming a coalition government. But the 2-party system is what we have. And it's ignorant to not recognize and understand that.