Lately I've been thinking about interesting things you could experience using virtual reality equipment that aren't actually virtual environments. I mean, you have this suit or helmet or plug in your spine or whatever that can give you any sensation you can program, why not program something really interesting that could never be felt out here in reality. There could be whole libraries of sensations to be experienced, all unexpected and consciousness-expanding.

A particularly odd one (which might be pretty disturbing if you weren't prepared) would be to have different temperatures on different parts of the body. Maybe a grid of five centimeter squares layed out over the skin, like a chessboard. The black squares would be very warm, and the white ones would be very cold. This by its self would feel profoundly strange, but even better, every five minutes or so the cold ones would fade to hot and the hot ones would fade to cold in a smooth gradient, causing interesting tactile confusion. Another possibility would be to have the environment be at a uniform temperature, slightly warmer than that of your body. You could then program two "snakes" of cold temperature to glide all over your body. You would feel your skin warming back up after one of the snakes passed, and then another snake might cross over the same section of skin, making it instantly cold again. There are lots and lots of variations on the temperature idea, too, so there'd always be hackers coming up with new ones.

True synesthesia would also be cool. Creating a visual representation of the sensation of getting your back massaged, or a sonic representation of what your taste buds experience when you eat Ben and Jerry's. I don't mean a pretty little shape you see on a black background, or a noisy sound you can sort of make out, but instead, full sensory crossover, to the point of excluding any other way of feeling those things. A beautiful shimmer of color, without blinking or eyelashes to obscure your field of vision, that completely and perfectly describes what the hands on your back are doing. A resonating, crystalline sound, with harmonics that explain the sweetness, saltiness, bitterness, and sourness of the ice cream with perfect clarity. Because of the depth of sensation needed to make this possible, only simstim style VR gear would work.

Powerful sensory deprivation would be easy, too. Instead of the background heartbeat, digestion, moving eyes, the taste of saliva, etc, send the neurological equivalent of a pure black signal to all of your senses. All that would be left in your reality would be ego, with no feedback except that occurring between neurons in your brain. Nothingness, nihil, the personal realization of zero. This might easily lead to insanity, if taken with any duration at all; I'd give myself two minutes, max.

A variation on the sens-dep theme would be to black out all of the senses but one, with it made profoundly sharp. Imagine, for instance, experiencing a roller coaster with only the sense of sight, and with the visual acuity of an eagle. Imagine a concert given by the New York Philharmonic, experienced only with a sense of hearing able to distinguish each individual stroke of bow on string, each whispered movement of the conductors baton. Imagine a rave with hyper-sensitive touch. Acres of lush garden with a preternatural sense of smell. A five star restaurant with a singularly perfect feeling of taste. This would be all of the best parts of sensory deprivation and sensory overload put together.