Maybe the blog that is hosted on a Nintendo Wii. It’s not the most practical hack but I find console modding really neat and the “because I can” style projects are particularly fascinating to me.
Some other favorite hacks are a bit more practical and have to do with extending the life of existing products. RebbleOS, for example, is an open source firmware that took off after Pebble shutdown following their acquisition by FitBit in 2016. It’s allowed people to continue using their e-ink Pebble watches largely unchanged. They can still do things like fetch the weather and voice dictation.
I think it has a bit to do with a lot of firmware or drivers being closed source too. I feel like a couple years ago I ran into that issue with camera my old Android phone had