Tables in wrestling are made from an extremely thin chipboard. It can support carefully applied weight, but with a little force, the table will snap in half.
They're not without risks, though, as they're supported on metal legs. Moreover, even the announcer tables are constructed like flat-pack furniture for performers to go through.
Kendo sticks are modified to look more painful than they are. Made by taping hollow bamboo sticks at each end, they produce a cracking sound and soften the blow.
Wrestlers also strike on a larger surface area like the back or front torso to dissipate the pain and reduce the chances of a shot hitting a protected region and causing injury.
The trash cans in wrestling are made from aluminum or tin for malleability and reduced weight. They are no thinner than soda cans, so they appear more painful than they are.
Since thumbtacks cannot be faked, wrestlers land on them with a larger surface area to reduce pain. Mick Foley stated that removing them hurts more than receiving them.
Barbed wire is often the real thing, though blunted for safety. However, Mick Foley wrote in his autobiography that it can also be gimmicked by using rubber tips for the barbs.