At one place I worked, a group of us would go to the pub almost every lunchtime. One guy always made sure he was never the first to arrive, so he didn't have to buy a round. He would stand with an inch of beer in his glass, untouched, for ages rather than get a round in.
One day, my mate and I spotted Tightwad walk into the pub before we got there, but when we got in, there was no sign of him. He was hiding in the bog, waiting for someone else to turn up and start buying the drinks. On another occasion, we spotted him duck into a phone box on the corner by the pub, so he could wait there until someone else arrived.
Every now and then, I would call him on it and just tell him it was his turn to buy a round. He never had his wallet on him, naturally, so I used to lend him the money. In fairness, he always paid it back the very next day.
He eventually got together with a friend of mine, who was also notoriously tight. We used to joke (privately,of course) about how the hell would they ever go for meals/drinks when they were both so mean.
One day, they rocked up at the pub where my ex and I were having a drink. We struggled to keep straight faces as they proceeded to argue, because they had both left purse/wallet at home. She blinked first, and "found" her debit card in the pocket of her bag and paid for the drinks.
What was weird about him though was that he was very generous in other ways. He'd do anything for you, came and helped me decorate, looked after my dog when I had to go to hospital, was happy to give lifts even if it was out of his way and stuff like that. It was just the buying drinks he was tight about.