Sometimes, I like to wait on the a cappella wars, but these guys clearly won the Internet this year. Six13 doing a perfect a cappella Hanukkah cover of Queen's "Bohemian Rhapsody" (they're a little loose with the history, but still...). Worth it for the a cappella guitar solo alone. Six13's "Bohemian Chanukah" can be yours from Amazon and other digital retailers.
Like Six13, the Y-Studs went the Queen route. But they do deserve credit for covering songs from the Freddie Mercury catalog that were not "Bohemian Rhapsody". The Y-Studs grew out of the a cappella group from Yeshiva University. They haven't been involved in the a cappella Hanukkah wars as long as some of the other groups, but they've turned out some super quality efforts in the past few years. "Don't Stop Me Now", which you can find at Amazon, adds to their Hanukkah legacy.
Unfortunately, The Maccabeats, who started the a cappella Hanukkah wars with their "Candlelight" video back in 2010 (which still slaps, btw), fall into fourth place this year with "I Have A Little Dreidel" done in many different musical styles. Some were very good--I'd love to hear a full Blues version (and the Gospel is super cool). Some not so much (I'm not sure they have the whole Bluegrass thing down). And, hey, they managed to get their Queen on at the end of the video. But, though The Maccabeats are very good and have a solid back catalog, they got Macca-beaten this year. Grab the group's 2018 Hanukkah single at Amazon.