Without doubt, Taito's Bubble Bobble was one of my favourite arcade games in the mid-80s. For me, I could think of no better way to use those 10p pieces. The versions that made it onto the home computer never quite hit the mark - although I understand the NES version wasn't too bad.
The objective was simple: take Bob and Bub through countless screens of baddies, capturing their foes in colourful bubbles and bursting them as quickly as possible. Take too long and a bad ass fish-like thing appeared to chase you round the screen!
I think it was my first experience of two player co-op - a feature I now always look for in a game. It was 100 levels strong (apparently). Sadly, I never got anywhere near that far - I'll put it down to my tender age at the time and shortage of coins - but I still had a blast.
It spawned numerous sequels, including the hit Rainbow Islands. Many years later the two little fellas even starred in another classic, Puzzle Bobble. But nothing, in my humble opinion, ever lived up to the original.
(Photo credit: HeyGabe)