A guy I worked with figured out that you can negotiate everything, and did. He'd get pissed off at the bank charging him an overdraft fee and sit in the telephone queue to get his £20 back.
He took a cab on a business trip to Dubai, and the cabbie kept the meter going while filling up. He argued it and got the equivalent of 50p off.
He'd negotiate agreements with brokers and negotiate absolutely everything.
He pushed really hard on the partnership agreement.
In the end it was just toxic and people were turned off. You don't want to end up in a long conversation every time there's something to negotiate. It also makes everyone think you're going to be difficult.