So I just witnessed an amazing glitch! If two players grab the spark at the same time, it will give the spark to both players allowing two rift dunks per run! This glitch looks like it is based off of a lagging connection so maby you could have more than two at once!
here's a link to a Video of this from reddit:
http://xboxdvr.com/gamer/Foople490/video/10455826
here's a link to a Video of this from reddit:
http://xboxdvr.com/gamer/Foople490/video/10455826