On this page you can find some pretty cool sample bots.
The @GmailBot was recommended by Pavel Durov himself. The bot allows you to get your Gmail mails as a chat message and you are even able to reply to mails from the chat. In case you want to disconnect the bot from your Google account, open this website and remove the access.
There are a lot of automation bots on Telegram. The famous IFTTT bot, Integram, Integromat, Zapier, etc.
The @StrangerBot was one of the winner bots from the Telegram bot contest in 2016. It allows you to chat with strangers.
Thanks to giphy.com's API, you can send funny GIFs to your friends. Try @gif in one of your chats.
Coub is YouTube for video loops. You can take any video, trim the best part, combine with other videos, add soundtrack. It might be a funny scene, movie quote, animation, meme or a mashup of multiple sources. @coub on Telegram.