I love messing around with extra dimensions. I enjoy crafting worlds with a little MORE, and when I am playing a supernatural or supers...or supernatural supers game all bets are off. I go hog wild in bending space in time.
Take one example. I was playing a game set in a college dorm where all the players were exposed to an explosion of a powerful being much akin to an angel. This semi divine agent embedded pieces of itself inside of them...altering their auras and allowing them to interact with spirits, the underworld, and to alter the real world with unique supernatural powers.
Here is where it gets weird.
They could access a type of copy shadow space they called E-Space. Ethereal Space that was like a shadow dimension that allowed for realtime travel. They trick is E-Space allowed them to bypass walls, move around most physical objects like they were ghosts. In fact most ghosts (or beings that were echos of the living) were found here. This was also where a lot of power players from the 'other' dimensions like Angels, Demons, godlings moved around with out being seen. THEN they could in E-space access another more advanced dimension. A-Space which could be accessed from mirrors and folded shadows. This other realm was disconnected made up of tunnels of light and windows into other worlds. This byway was how the PCs and NPCs could bypass travel distances and pop in and out rapidly over great distances. As time when on the group cross trained on these 2 methods of travel and their other ghostly powers and started getting really good at popping in and out at great speed. They loved it. It was a big mystery where the next mirror went to.
Think of oWOD, Umbra on steroids.
I also loved CyberGeneration's Viruality and the old Cyberpunk cyberspace universes. I always wanted to explore these digital worlds with my PCs. Go scampering over data vaults and having chats with AIs. Or maybe in Shadowrun a Mage using spirit sight always looking around at auras and local spirits, in a half here half there drugged out blisful look as he's a otherwordly tourist.
I think it reached it's peak in Planescape. Jumping through portal keys, diving down the Astral, then dealing with the Ethereal and Inner and Outer layers. Weird places like Bytopia and Mechanius pulling me in every time. And Limbo, for love of Limbo.
I enjoy opening portal to the Labyrinth of Exalted, drawn to Stygia to gloom over the Vaults of the Neverborn. Then to walk 5 days to reach the edges of Malfius's great Yozi bloat. Finally to sail the quicksilver rivers of Yu-Shan before stumbling out the heavenly gate winking at the confused Lions. I'm drunk on other dimensions, alternative planes.
I've actually explored Hammer Space once. Stepped inside my own internal Katana folded space time ala-Highlander and stumbled across mountains of old gear I forgot I had stashed there.
I want to draw chalk lines on the street, knock 3 times, and then open doors to bizarre urban playlands.
I want to tear open nihils and dance with reapers.
I wanna get around.
Sorry, I'm drooling a little.