RightGIF - Less noise, better GIFs. A better /giphy for Slack.
Firesong - Giphy for Music in Slack w/ Emoji Search
Slack Meme Bot - Spice up your team conversations with memes
SnipandShare for Slack - Quickest way to share bugs, ideas, links or gifs to Slack
My Slack Emoji - Turn your team photos into Slack emoji's
VixT on Slack - The best video mashup app now on Slack.