The Wub Machine - Turn any music into Dubstep, Drum & Bass, and more.
Firesong - Giphy for Music in Slack w/ Emoji Search
The Eternal Jukebox - For when your favorite song just isn't long enough
Slack Meme Bot - Spice up your team conversations with memes
YOU.DJ - Mix SoundCloud music and Youtube videos live in your browser.
VixT on Slack - The best video mashup app now on Slack.