I haven't seen this one mentioned yet: Chef's Press. They're interlocking stainless steel weights.

I was a bit nervous buying them as they aren't cheap and I wasn't sure how often I would use them but they've proved to be one of my most used kitchen gadgets. I use them a few times a week.

They're great for keeping steaks in contact with the pan when searing or keeping bacon from curling up. I use them to weigh things down in water for thawing or cooking in the sous vide cooker. They're good for pressing cheese or tofu.

They have built-in handles that make them easy to pick up, stack, and interlock.

They're dishwasher safe.

Perfectly designed for their job.