1960's and 1970's lego wheels had a small embedded metal axle. Depending on orientation these could cause a significant puncture wound:

https://www.bricklink.com/v2/catalog/catalogitem.page?P=7039

Never had any of these but I suspect this variant would be even worse due to the smaller area at the tip of the axle:

https://www.bricklink.com/v2/catalog/catalogitem.page?P=7039...