Is it ethical to downvote answers so my question is unanswered again? In my specific example here, I have two answers, each with one upvote, neither of which seem to get the point of the question (if you can improve the phrasing, please go ahead). Would it be ethical to downvote them each so that my question show as unanswered again? Is this an effective tactic to get my question answered, short of a bounty? I will happily do a bounty as soon as it's available.
Considering that both answers overlooked the bug in the code sample you posted, I believe it is fair to downvote them. Now, on the other hand, a new answer has been posted to your question, providing you with the solution to your problem! Go ahead and upvote + accept that!
Shame on the unicorn for covering the name of that shameless rep. whore!!
It might be unethical if you only do it to make your question unanswered again. But if the answers in question weren't actually helpful, then a down-vote is never unethical (it's even in the tooltip text of the down-vote button).
So in this particular case, just go ahead and down-vote them. No harm done.
Downvoting for some gain when you wouldn't otherwise downvote is probably a bit dodgy (but then, I'm a bit of a purist). I'm sure people do it, though (to push up their own answers, for instance). But you're free to downvote any answer you don't think is helpful (on your own question or others). You clearly don't find these two helpful. So the question is: Would you downvote them if they each had two upvotes and it wouldn't have any effect on your question's listing?
I don't know that putting the question bakc in the unanswered state is really going to help, so downvoting just to get to that state may be considered unethical, but worse - it probably won't even help.
Address the answers in a comment as to what they did or didn't help with so when others come along and read them they understand why they aren't helpful.
Downvote them if they are unhelpful or wrong.
Consider rephrasing your question to make it more clear and easy to understand/read - this will also bump your question.
Bump your question a few times until you get an answer (or people complain that you're bumping it) by editing the question in small ways.