ScrapLeague is a 1v1 arcade robot fighter that plays right in your browser - no download, no account.
You pick a chassis, a weapon and a gadget inside a power budget, then fight 90-second rounds above a glowing pit. Driving is aiming: you only hit what is inside the cone in front of your nose. Hits from the side wreck the drivetrain, hits from behind wreck the gadget, and a destroyed part falls off for the rest of the round. Push the other one into the hole in the middle and it is over on the spot.
Eighteen parts, three AI brains, a five-round tournament, practice targets, a local duel on one PC (mouse versus gamepad), twelve achievements, replays and a shared leaderboard. Everything single-player runs in the browser, on a phone as well; online 1v1 is in the Windows download.
It is free and in early access. There is one thing I would really like to hear about: light bots against heavy bots. In my own measurements a heavy hammer bot beats a fast light bot almost every time when the AI plays both sides, and I want to know whether a human does better before I change the numbers.