Any suggestions on getting a blade off a lawn mower. I spent about an hour with a can of WD-40, ratchets, vice-grips, a hammer and I can't get the bolt to budge. Any secret tips out there? It's a standard 21" Murray push mower for reference.

Wrong tools.

https://www.askmehelpdesk.com/tools-power-equipment/honda-harmony-mower-blade-removal-214511.html?highlight=blade+removal

Actually a 1/2" breaker bar is better. Pipe wrenches can be used to hold the shaft, but not recommended.

Impact wrench and impact socket is ideal. You can probably rent one (Electric or air).