Dictionaries

Dear People,
I am a person interested in english dictionaries. This may sound strange but it is just as it is.
I have about 7 dictionaries on my computer. To count: Macmillan, Meriem-wbester, random house, new OESD, OED, american heritage, collins.
Very dictinary has a superior feature over other.
Some have thesaurus, some provide phrasels, some provide sentences where the words are used in, and some provide etymological knowledge.
Now, I would like to discusss this isue here.
- Which dictionaries do you use?
- What others can you recommend?
- An important question for me is: For academic purposes, which dictionary is essential?
- And we can discuss the issues around.
Lets detail this, and we can all benefit from recommendations!