During this drought of online multiplayer games, we were grateful for a tip-off from reader Aleksander Kiin, linking us to Teewars.
Despite appearances, it's nothing like Worms, so no need to worry there. It is in fact a super-cutesy 2D shmup, with four standard weapons, one very cool bonus samurai sword, and a grappling-hook-chain-thing on the right mouse button for making those awkward leaps.
Once the chain is mastered moving around the maps is lots of fun, making it all the more satisfying when a rocket lands smack-bang in your opponent's chirpy face. And then you realise you can fire the chain at other players. It's free, and there are a people playing on the servers even first thing in the morning. Certainly worth checking out.