There are three or four commentaries I find the most valuable. I like them because they are concise in their reasoning, very sound in the reasoning(not able to be disputed very easily), and give, trace how others came to an understanding of the text(though not all do this).
Here is my list of commentaries I probably use the most.
MacArthur's New Testament Commentary
Baker Exegetical Commentary of the NT
The works of M. S. Mills-this was a little unknown to me until I did a search of every resource that speaks of a particular passage. He has commentaries as well as study guides.
The College Presss NIV Commentary.