When it comes to anti-heroes, Punisher is simultaneously the most simple, and the most crazy.
A war veteran, Frank Castle took his family to a nice day at the park, only for things to turn tragic once they got caught up in a gang war, Frank's family getting caught in the crossfire, and getting killed as a result. As the sole survivor, Frank swore vengeance on crime, and started a one-man war against criminals. This has led him to go to extreme lengths, becoming a pariah to the superhero community, and coming to blows with them on more than one occasion.
But even with this seemingly simple premise, writers have thrown Castle in a million different directions in order to keep the character interesting, and have used the Punisher in ways that were completely unexpected. Alternate versions, crazy storylines, it doesn't really matter, the Punisher has been everywhere in some of the strangest forms imaginable.
10. War Machine
During Frank's long, long war on crime, he has used some unique and wild weapons. After all, the more firepower he has, the easier things can be, and the happier he is (at least as happy as Frank can be).
So when Nick Fury approached him with a mission to stop a psychopathic general, there was one weapon he needed to make sure he could get the job done; the War Machine armour.
Putting someone like Frank behind the armour made him almost unstoppable, and he knew it. Which is why he went rogue and decided to keep the armour himself, using it to fight the criminal underworld back in New York City. With him almost causing an international incident and with the fact he had the armour of a beloved figure in the superhero community, plenty of costumed heroes came after him.
While the run was relatively short-lived, it was a fun time for Punisher fans.