What is the most extensive/best thesaurus?

[postdeborinite]

When I am writing and need inspiration in how a sentence can be varied, I use Thesaurus.com. However, I have the feeling that this is not the thesaurus that the "pros" are using. My key criterion for a good thesaurus is that it is extensive. What are you using? Both digital and paper-based suggestions are welcome...

[Tdol]

I am not a great fan of them- they tend to clump words together and people use them as if they were synonyms when there are differences of meaning or collocation. However, have you tried OneLook's reverse dictionary: OneLook Reverse Dictionary

[konungursvia]

Roget's. But as Tdol said, they're only useful if you already know the words you're looking for. Don't use it to pepper your English with appearances of lexical variety.