Moveable soccer goals can cause serious injuries if not installed or anchored correctly. Make sure the goal is manufactured according to the relevant Australian Standard and that it's securely anchored during use.
People are at risk of serious injury when using a poorly-secured basketball ring for slam dunks. Always make sure your basketball ring is installed appropriately and carries the mandatory safety warnings.
Friction burns are a common risk when using a treadmill, including burns serious enough to require skin grafts. Make sure you buy a treadmill that features a safety stop switch and always follow the manufacturer's instructions.