Here are some plugins which could help you build out your own or serve as a reference point:
- IsPrime https://github.com/lvonkacsoh/Flow.Launcher.Plugin.IsPrime
- RollDice https://github.com/lvonkacsoh/Flow.Launcher.RollDice
- FancyEmoji https://github.com/Ma-ve/Flow.Launcher.Plugin.FancyEmoji
- Steam Search https://github.com/Garulf/Steam-Search
- Currency Converter https://github.com/deefrawley/Flow.Launcher.Plugin.Currency