Slack Singles: /Stocktwits
StockTwits is a fan favorite for watching/tracking public markets and the news around them. A few weeks back they introduced their Slack Slash Command integration.
When you enter /stocktwits [symbol] it pulls in a ton of handy info with Red/Green indicators for daily performance and a GIF reaction.

What they got right
The combination of color coding, emoji and a reaction GIF feels right at home in Slack. All of the GIFs seem to be under 2mb, meaning they always expand 🎉.
Additional info like the market cap, year and day range of the stock is also helpful to apply some context.

Room for improvement
GIFs can dominate a feed, short of using the /collapse command there are no integration settings. The integration is built on Giphy which has a history of being very hit or miss.
Pro tip: use the /collapse command to hide GIFs
There was also a brief stint where StockTwits would post breaking news links but I have not seen that in a while — hopefully that returns.

At Robin we have a channel dedicated to talking about the market so this integration fit right in. If you have similar conversations in Slack this integration is a big 👍.
Custom Slash commands are a fairly new feature with Slack, given that it turns the messaging app into a command line interface with other services. I try to highlight the standouts.