Depends on where I am. If I'm not at home, I've got a Mac Book Pro that I use; going on a year old. If I'm sequestered in my code cave, then I've got a custom rig I built running Win 10 on 16GB of RAM, a 3TB HDD, an Octa-core AMD processor clocking ~4GHz/core, and a modest vid card pushing display out to an LCD TV via HDMI and a smaller monitor on the side that I use for showing reference material, notes, stackoverflow searches, etc.