2-methyl-2-butanol. It's a tertiary alcohol used in industry and as an RC alcohol.
2M2B had no hangover because it has no toxic metabolites. It's a good drunk too.
I liked it at first, but grew to dislike it, and tossed the rest of mine. It lasts way too long. I found it had a hangover of sorts, though I think it was actually just that I kept feeling it through half or more of the next day, which made me feel off and unpleasant. You're right it has no toxic metabolites, so in that sense it's safer than alcohol. But it's extremely potent, and can kill you in an overdose. It also tastes and smells HORRIBLE, and there is absolutely no way to mask the taste. I dosed it by putting it into the largest size gel caps with a syringe (which is how I measured it to dose, the syringe, which is 100% necessary), which it won't immediately dissolve. So I barely had to taste it (though some of the taste seems to seep through), but then the burps... horrible. It tastes like nail polish remover mixed with mint mixed with poison, and so do the burps. I found the high less euphoric than ethanol, and more sedating, and more dissociating. If I could wake up and feel normal, I'd like it better, but instead, most of the next day is weird. And there is an urge to redose, like with alcohol, but not as strong, which is quite dangerous when it comes to a very long lasting alcohol which is also easier to overdose on.
Ultimately I don't recommend it. If there was a tertiary alcohol with no toxic metabolites that lasted around as long s ethanol, or a little longer, that would be great. Actually there sort of is, though it isn't an alcohol... it's GHB/1,4-butanediol/GBL. But unfortunately, GHB is way too good, and I can't control myself on it at all. It's actually WAY more euphoric than alcohol and isn't toxic (1,4-butanediol is probably a bit toxic though - for those unaware, it's a primary alcohol that is converted via alcohol dehydrogenase, into GHB - but nothing compared to the toxicity of alcohol (ethanol)).