I prefer a small, lined Moleskine and a blue Zebra F301 pen. Being able to write things at moment's notice is invaluable.
I'm a fan of Mirra by Herman Miller - it's pricey though (although affordable if you consider its warranty - buy 4-5 $150 chairs over 10 years, or just one $700 chair) .
Also had good experiences with a few Office Star chairs (the higher end ones, around the $200 price point)
For people working with computers all day, having an ergonomic, well adjusted chair is paramount.
I have several Herman Miller Mirras in my office. They're every bit as good as the Herman Miller Aeron, just a lot cheaper and easier to adjust.
I always carry duct tape, WD-40, swiss army knife, another knife, lighter, a spare CAT-6 net cable. Also recently I started to carry those small bags with sugar that they give in coffee shops. Funny thing is, that run into situations where duct tape is needed almost on daily basis. It's like the "when only thing you have is a hammer..." effect, but in a positive way. Opportunities to fix/hack things find you all the time ;).
EDIT: Fixes grammatical error
I have a bunch of 1' m/f power cords, for keeping wall-warts from taking up too many spaces:
I also picked up some of these with a right angle passthrough connector - you can put them into a wall, cord comes out parallel with the wall:
Great for small clearance areas.
It has actually turned out to be very useful as I keep flipping the breaker when I forget that I can't run the coffee maker and a space heater or microwave at the same if they are plugged into the southern half of the apartment...
I have also had a cheap Smith & Wesson knife for new gadget unboxing for several years now.
Interestingly for me, is that the phone probably doesn't draw as much attention and envious looks and comments (in my circles anyway) as my not-red Swiss-army knife (big and small blades, tweezers and toothpick, bottle/can opener, screwdrivers). EDIT, not that this is of any use for computer hacking, sorry, got sidetracked.
It's a Leatherman Skeletool CX, FWIW.
Simple, gorgeous and can be taken anywhere.