I would say, 2010. My LibDem vote helped give the LibDems enough seats to enter a coalition Govt with the Tories. Now, looking back, am I proud of this? Well, no. With great power comes great responsibility and I regret to say I did not use that power wisely.
So, are you arguing no votes have consequences, therefore there is no point in voting? If so, why are you taking part in a thread on a matter which for you has no consequence?
In my view, your and my vote is part of a collective. If no individual takes part in voting for that collective then there is no collective. If individuals opt out of the voting process then that collective is diminished. Voting is an expression of the will of society at a precise moment in time. A snapshot into what society is thinking and feeling, be it for good or ill. Each vote has consequence because it forms part of that snapshot in time. Add those snapshots together and you can detect trends, see where the society, of which we are all part, is heading.
I can grumble about the voting system and where I live etc, but I still vote, because my vote is my expression, my contribution to what I think is important. Your belief in the value of nothing is too nihilistic for my tastes.