"Most people safely assume that not just claw machines, but entire arcade attractions from shooting galleries to those 2p coin pushers are heavily rigged."
The 2p coin pushers are based on a bit of the money going down the side. Shooting galleries are about trying to hit things that are rounded. Legit, but a bit of a trick (and you lose because you're a mark).
The only gamble that works is getting on a one-arm bandit after someone has just dumped a large amount of money in and got nothing much back. The machine is below the payout percentage and will pay.