I personally use Wunderlist and have been an active user for around 4 years. It's the only to-do list app that really helps me complete my tasks, both professional and personal. It's very easy-to-use and you can sync between all your devices - Macbook, iPhone, iPad and so on. I love how simple and also flexible it is.
Wunderlist offers way more features in their Free plan. Todoist is also a great task management tool that I still use sometimes for some cases, but Wunderlist definitely offers more in the Free package.
It's a great task management tool both for professional and personal life. You can use it to set due dates for your tasks and get reminders whenever you want. I think it's great for small teams and for personal use. It's probably not suitable for larger companies.