Normally I don't keep anything permanently where I'm working, but I almost always have a backpack with me - something to carry my lunch, water, notebook, etc. to & from work.

So rather than a specific get-home-bag, I usually have some contingency gear in my day-to-day backpack. Currently this includes:

• wind-proof gloves & toque
• water-resistant wind jacket
• small FAK
• altoids sized emergency kit
• emergency blanket
• altoids sized repair kit
• toilet paper
• AAA flashlight
• small sharpener
• lighter
• a PowerBar

This changes from time to time depending on what I've been doing (e.g., did I put my emergency kit in a different backpack for camping and not put it back come Monday?), but generally speaking this is the type of stuff I'd have.

The addition of these things doesn't eat up much space in my bag, my lunch, notebook, and water take up most of the used space, but they are nice extras in case something does go south while I'm out at work.

Something I also try to plan for is the possibility that a building evacuation could be needed when I'm not at my desk. For this reason I try to ensure that I won't be stranded with only what I have on my person. For example, I always carry my vehicle keys with me and I try to always keep a couple transit tickets in my wallet.