Aside from using tools to fix or reinforce your shelter, you might need them to escape your shelter. A lesson learned from 9/11 is that exits can be blocked by fire and debris, requiring rescuers to force/cut their way through locked doors and walls to get to survivors.

Perhaps not a problem for you, but I work in a high-rise, so water is a concern. I keep a 2.5 gallon container of water in the bottom drawer of my lateral file. I'm thinking of adding a second.

Also, consider your co-workers when stocking-up. A sad reality is that most won't have any supplies or gear. I have a couple of Costco-size boxes of granola bars and a box of Clif bars in addition to my personal supply of food so I can share without impacting my own needs. Ditto for cheap flashlights (a recent addition due to another thread here).

In addition to flashlights I have a dozen 12-hour chem sticks so I can provide a little general lighting in places like dark hallways and bathrooms without wasting batteries on flashlights.

The comment about rain gear should be reconsidered. If the building's sprinkler system is activated it will rain inside. Also, if there are any hazardous materials in the air, a rain poncho can help provide protection. A rain poncho can also be used as a wind breaker if the building structure is compromised.

As for cell-phone chargers, I have several cheap, 2xAA emergency charger with a USB port. Using lithium AA batteries, it will completely charge my iPhone 4 in about 4 hours. I keep an Otterbox full of lithium AA, AAA and CR123A batteries to power all my emergency electronics for the duration.

You would be surprised how few businesses have battery-powered radios. I keep a solar/crank radio with AM/FM/WB plus an LED flashlight in my kit.