Yeah, the Cosmo-Knight was pretty tough. I played one almost 10 years ago in a space-based Phase World campaign, back when playing the Palladium system didn't automatically cause me to break out in hives.
Another crazy combo I heard of was a Demigod with a Heroes Unlimited martial arts class. I forget what the class was called (Ancient Master, maybe?), but the gist of it was that the class started at level 15, to represent a long life of studying the martial arts (think Quai Chang Caine). The funny thing, though, was that a Demigod could select the class abilities of several spellcasters, including the Ley Line Walker, and he automatically knew all the spells for that class equal to his level. So such a character could, quite literally, start out a campaign knowing every single spell there is in the game for the Ley Line Walker. Though from what I understand, that was nerfed. Still funny as hell, though.