A Kool Kartoon
One of the most rare Mega Man releases ever.
But in all seriousness, the NGPC version of these arcade games has been hard to come by for collectors for age, so it's good to see it!
*Update: These games are literally the original JP ROMs. Granted, you don't really need to understand what's going on to play these games, but just thought I'd give a heads up before people download.