what do you mean by "best icon set".
it really depends on taste there are some very nice sets out there.
personally i use ayecon because i really like the minimalistic yet expressive icons in that package and also because they are flexible enough to fit in with a wide range of other icons as long as they are decent enough - even if 100+ are already fitted for that package.
additionally, and due to its flexibility there are alternatives you can find and with minimal edit effort you've made yourself a new ayecon icon.
elite 6 appears to be the taste of the week, though. jaku is really nice but a pain to look at if you have unformatted icons for that setup.