Never worked a job that led to me getting tipped(though I did get 5 bucks for making a cheeseburger just right at mcdonalds lmao) But I have tipped as much as 150ish percent for excellent service before.
My younger brother was at a wing place and didn't have enough cash on him to tip. He told the waitress that next time he was there that he would tip her. She obviously wrote that off in her mind that she was never getting that tip. 2 weeks later he was there, tracked her down and tipped her 20 bucks. Made her night.
About a year ago I was at a dairy queen and of the 5 or so employees working there was one girl clearing working harder than the other 4 people put together. I asked the cashier to have her come to the front counter. She was extremely confused but came up to talk to me. I handed her the 5 bucks I had in my wallet and told her I could tell she was working extremely hard. She told me she was having an awful day and thanked me several times. She nearly started crying and came around the counter to give me a hug.