Usually just a rag, mabye one with some Wd40 on it. Ratchets, sockets, wrenchs, screwdrivers, etc... get wiped down before I put them away after I'm done with a job. The floor jacks gets brushed off about once a week since it's next the the wood stove and gets ash on it quite often. Air tools get oiled about every three weeks (more often if I use them allot, less so if no use).
I find that a rag with some Wd40/CRC Power Lube on it does quite well. Not soaking wet with it...just a very light coat. Enough to get the grease off, but not so much as to make the tools slipery.