This is the best battle royale experience in anime. Does pretty much everything right that you need to pull a good BR off - a diverse cast of characters with unique/strong motivations, great dialogue full of memorable speeches (i.e Rider's speech to Saber about true kingship), a dark tone that coneys what is at stake for the competitors should they not win, detailed strategy and preparation dictating how fights are won. Main character isn't some naive teenage boy fighting for "justice" only to realize it doesn't really exist. Kiritsugu will win by whatever means necessary even if it means sacrificing everything around him. He is more or less the reason Fate/Zero shyts on UBW and their immature children mages. Also Saber being turned into a complete joke at one point tied up in a wedding dress doggy style position for NO reason but for fanservice.
Any argument for UBW being better than Fate Zero should die with this. Forever.
Giving Fate/Zero a 9 bordering on a 10. I'd probably give UBW a 6 if it got on the poll.
Since we're still going and I have no idea when we'll stop, if we stop, want to nominate -
Welcome to the NHK
Prison School
FLCL (not alternative or progressive though)
Original FullMetal Alchemist...guaranteed to qualify, everyone should have seen it, probably gonna be a controversial poll. I think its better than FMAB in a lot of ways
Full Metal Panic. Kinda iffy on whether or not enough people have seen it to qualify. but worth throwing out there.