The biggest calf I've ever personally seen was a flower-power colored fullblood Simmental out of a first calf heifer. The calf was dead and we didn't weigh it, but it was easily 150-165 pounds AND it was a HEIFER calf!
A friend had a really good herd of registered Holsteins and the absolute biggest calf I've ever heard of was from his herd. The cow was 28 days overdue and he simply thought she was due to another AI date that he'd forgotten to write down. He palpated her, the calf was alive, knew it wasn't coming out by the conventional method, so he called the vet. The vet was in the area and even had the joy of having another university vet with him and vet students that were shadowing. Both vets are awesome! They do a great job and are super people! Did a C-section and the university vet TRIED to pick up the calf. No luck. It took the whole group to get the calf hoisted out of the cow. ...186 pound heifer calf, dead by this time. The pictures are amazing!