I have an electric lawnmower that I custom built. After years of reliable service, it needed a complete teardown and rebuild. It's powered by a 2HP induction motor and one of the features I wanted to add to it was an electronic brake. That way the blade stops quickly whenever the dead man switch is released.
I've had a little 12 ft (3.28m) aluminum boat with a 6 HP Johnson outboard for years. The motor is big enough to get from point A -> B but not big enough to push the boat up on plane if I'm the only one in it.
Our house has a large double sided fireplace right in the middle of it. It has a vent above the doors on either side to circulate the hot air, which is not all that effective. I wondered if it would help to have air forced across the firebox and decided to try an experiment. I rigged up a window fan to blow air into the vent in one room.
What do you do when you have a pretty comfortable swivel chair but want to move it around like an office chair? You bulid a six wheel flatbed trailer for it.
If you want to buy a new lawn mower, you can go down to your local big box retailer and find that most of the available options are probably battery electric mowers.
That was my first attempt at electrifying a gas mower. I used a 2 HP induction motor attached to a mount designed to be a drop in replacement for the engine. The first version used the frame from a Troy Bilt front wheel drive mower. This one only had a single speed transmission and couldn't handle the added weight from the motor. I think I used it for one season before replacing it with Version 2.
I just noticed this community in the "Trending" box on my home page. I love the premise, and am looking forward to seeing what people post. I'll try to remember to post as well, if I do any interesting DIY projects.