Cast Your Vote - Cast Your Vote is an app that allows you to set polls and a voting system and know the answer to your question.
Simple Poll - The easiest way to create polls in Slack
My Vote - My vote is an app that allows you to create ranking, ratings, polling contests, and view the results either after voting closes or in real-time.
GitHub Polls - Polls for GitHub issues and readme
Pollie - Create polls and share them via your favourite tools
Curious Polls - Answer a question once a day for the chance to win £100/$100