* It's the most fun I've ever had with a to-do list
* You can "quest" with friends to gain support and accountability
* It's free
* The UI isn't always the easiest to use, but I still think it's definitely worth it for what it provides
I've been using Habitica (previously Habit RPG) for years now. If you haven't tried it, you should. It's a fun and easy way to turn your life into a game and feel like you're winning at it. :D
Pro tip (from personal experience): If you find yourself with a lengthy task list that you never finish and just feel guilty about, scrap it and start over with smaller, actionable items. Life should be fun!