OK. We have a tendency in this forum to rabbit on about equipment that costs hundreds, if not thousands, of dollars/pounds/local currency of your choice. That's all very well and it's great to dream about owning all of these things but it would make life kinda expensive to go out an buy them all 
So let's try the other extreme... what bit of equipment do you have in your camera bag that you couldn't live without and cost you less than 50 dollars/pounds/euros/groats or whatever?
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For me, it would be the Sto-fen "Two-Way UNI" flash bounce adapter. It allows me to get nice, even, soft flash lighting at motor-shows with very high ceilings and often dodgy lighting. It cost me $20.




