ActionComplete is described as 'streamlined task management solution for the practitioners of GTD methodology' and is an app in the Office & Productivity category. There are more than 10 alternatives to ActionComplete for a variety of platforms, including Windows, Online / Web-based, Windows Phone, Mac and Linux. The best alternative is Remember The Milk, which is free. Other great apps like ActionComplete are Conqu (Freemium), todoMini (Paid, Open Source), Cheddar (Free) and MyMaelstrom (Freemium).
Qiknr is a simple objective to-do list. You don't need to register to get things done or some fancy email, calendar, multi-task agenda that takes so much time just to organise. Just assign the tasks you want, optionally place a time for its completion and start working.