2-Pack of Nitro-Strike Mini Foamer Fire Extinguishers (Fights Wood, Paper, Oil & Gas Fires) $10 + Free Shipping

These are basically unsafe -- foaming water isn't going to be a safe choice for an electrical fire, and does approximately nothing but spread a grease/cooking fire, so I'd rather just use a big bag of baking soda ($6 from costco) or an ABC dry chemical extinguisher (often $20-25 in multipacks for 2.5 pound, which is about the smallest you should bother with).

I had a small electrical fire at home (bathroom fan), used a dry chemical successfully to prevent the fire extending into the ceiling, and spent about a day cleaning up afterward. I replaced it with a recycled-Halon 1211 extinguisher for the electronics and a few 5 pound ABC dry chemical extinguishers for elsewhere. I'm still trying to decide between a Halon+ABC or just ABC for the car, since if it were my (insured) car, I'd just let it burn to a total loss, but ABC would be useful for putting out fires if someone is trapped in another car.

I'd recommend a $200 halon extinguisher (or maybe CO2) if you have a lot of electronics, and ABC dry chem for bedroom, kitchen, and garage. The extinguishers aren't just to save your stuff, they can also save your life.