United Kingdom

Here's a highly plausible scenario: the Tories get the most seats in the Commons, but not enough, even with any DUP they might be able to have "unofficially", to have a majority of parties that take their seats (I assume Sinn Fein won't do the latter, still). Labour+SNP, plus, maybe, Lib Dems, and even Plaid Cymru and the Green(s), or Alliance and SDLP, would be able to form a majority, under a supply and confidence agreement.

But if Labour rules that out with any party, what right would Labour have to be the government instead of the Tories? So we'd get a minority Tory government, that would be likely to be defeated by the fairly similarly voting bunch listed above, on a variety of votes. This would be that 'chaos', with, I expect, a new election not long after, to try and get a different result.