Well it would probably be useless because the material that portal surfaces are made of can be found (almost) nowhere outside of Aperture, but if I either had a constant supply of conversion gel or if I had an upgraded version that could shoot portals on any surface:
-Shoot a portal at the bottom of a playground slide and another one at the top and then slide down so I shoot straight up in the air. Assuming I also had long fall boots too, the fall wouldn't be very dangerous. If there was a wall perpendicular to the slide's entrance, I could slide down the slide over and over at a faster speed.
-Make money by providing people with an instant taxi service.
-Use it as a personal form of transport so I don't have to learn to drive or worry about polluting the air.
--------------------Legacy custom music
How am I so creative? I think taking walks might have something to do with it.
Every single level I will ever make in SMM2 will be easier than Ultra Necrozma.