I can think of a couple. Once on Mark Twain, we were working small crankbaits along a rip rap bank catching a few bass along with a bunch of big drum. I hooked a fish and it slowly swam away from the bank,staying down the whole time. My buddy and I were both thinking,.."yep, another drum..." . It stayed down until it got right at the boat and then rolled up on its side. It was a huge largemouth,Those ones that have eyes bigger than quarters. I reached down to grab it and it took off and before I could turn it , it pulled off. I don't know what it would have weighed but guessing it was a 9 or 10.
Another day on Thomas Hill we were a Poes 300 around an old bridge and had a good hit. I yelled for my buddy to get the net,thinking it was a 6 plus bass. A few seconds later I told him never mind. It wasn't a bass. It swam slowly towards the main lake with me following on the trolling motor. I would pull really hard to get it up with no luck. After about 25 minutes I felt it catch the line on a stump and it broke off. I have caught several flatheads in the 15-20 pound range , but this one was way different.