Frankly, given the ability of the internet to associate the most innocent of pastimes with the most emetic of pornography, it's amazing how low in profile many of these games are. The fact you're unlikely to be pissing about on XXX Pac Man in any civilised office doesn't help, but it's amazing how many people don't know they exist.
So enjoy: most are variations on old classics - arcade games with a 'reveal', so to speak - but all are good, unclean fun. All of these are free to play and don't require subscriptions or membership: be warned though, this is Not Safe For Work stuff...
Ben Warner