Discord.js - A JavaScript library that enables the ability to code a Discord Bot.
MEE6 - MEE6 is a multipurpose Discord bot with moderation capabilities, leveling, Twitch alerts, and an easy-to-use online dashboard.
Discord Bot Maker - Powerful bot development tool for Discord.
YAGPDB - YAGPDB (Yet Another General Purpose Discord Bot) is an advanced configurable Discord bot providing a load of features for help with managing a server.
discord.io - A small, single-file, fully featured Discordapp library for Node.js and browsers.
Arcane - Leveling, XP, ranks, voice, role rewards, auto mod, reaction roles, custom commands, YouTube alerts.