I like to do a fair amount of weird metagame stuff.
Our current campaign has taken on several incarnations: It started 700 years ago, when the PC's prevented an ancient evil from returning to the world. One of the PC's was turned to stone during the final battle, so he has survived to the present day and is a part of the current party.
Shortly before the gods were killed, the PC's were given the opportunity to Walk the Maze of Eshu, God of the Many Paths. They saw several key moments in history, spanning nearly 1500 years. They even saw themselves being killed shortly after the final battle of the campaign, and got the chance to ask a single question of their future selves. Of course, when we actually played through the final battle, they got to answer the same question they had previously asked.
I really like taking a break from the main storyline, and running a short complimentary game with new PCs:
I recently ran a D&D CSI game that was a lot of fun. We used a new party of PC's (a group loyal to the BBEG in the campaign) to react to some of the events started by the main party of PC's.
When I ran Return to the Temple of Elemental Evil, the PCs decided to seek help amongst the celestial court of Corellon. We ran a few sessions with the players taking over a group of angels sent down to help destroy the bad guys.
One of the PCs in our old Return to the Temple of Elemental Evil was reincarnated as a swarm of bees. This was after he had been identified as the avatar of an ancient evil, and betrayed the rest of the party (nearly leading to a TPK).
In our current game, the PCs have had to complete several pretty epic tasks in the course of their adventures. They had to dig a grave for a 200' tall giant in exchange for the reforging of a glass sword that had killed a god. They had to tell a new secret to an ancient goddess of hidden knowledge. One of the PCs is dealing with an unexpected pregnancy (after being unexpectedly turned into a woman).
Nareau