Now UI Kit - A beautiful Bootstrap 4 UI kit. Yours free.
RightGIF - Less noise, better GIFs. A better /giphy for Slack.
Dashboard UI Kit - A modern & responsive dashboard UI kit for designers.
Yarn for Slack - Drop TV and movie clips into your Slack chats
Landing UI Kit - Handcrafted UI components for landing pages
Firesong - Giphy for Music in Slack w/ Emoji Search