Bolo was a popular Mac multiplayer tank battle game back in the early 90s (predating the Web!). I played it a good deal in the computer science grad lab at Auckland University. It's probably the most fun multiplayer game I've ever played. The core gameplay was quite simple (it had to be, on that era's hardware), but team strategy and tactics got very deep and games would often get very intense. It didn't have the problem that has turned me off RTSes --- an initial "rush phase" that usually decides the game in the first five minutes. Skilled players could turn around an inferior position, but it mostly avoided endless see-sawing too.
I've been looking for classic games to play with my kids and yesterday I decided to see what had happened to Bolo. The original Mac version is long gone but a clone, Winbolo, was written for Windows and ported to Linux. It was shareware for a while but now it's been released under the GPL. There is actually no downloadable Linux client --- the port was not maintained --- but in a few hours of hacking last night I was able to bring it back to life. The gameplay feels great, closely matching what I remember.
Winbolo would be a great game to port to the Web. It's tons of fun, multiplayer, open source, and not very demanding on the client. The only difficult part (but it's a biggie) would be networking. Winbolo is client-server using UDP. You could use Websockets but that wouldn't be ideal. What we really need is WebRTC datagram support. Fortunately, that's coming!