1. Google Keyword Planner with MS Excel.
2. Market Samurai
3. Long Tail Pro
4. Keyword discovery
You could also try out Keyword Revealer and they do have a free plan as well as paid. They let you see google insights, moz and social metrics and domain availability too. Hope this helps you out in making your decision.
Does anyone know which keyword tool is best for keyword research and also if you have your favorite keyword tools list please share.