In my teenage years, I thought the world might appreciate a shampoo bottle that worked well as a self-service device. It would be a great design challenge. It would have to be subtle enough to look innocent, and yet be functional.
A subtle fleshlight... that looks like shampoo and also contains shampoo! One thing I learned about guys is they love combining things. ie: Old Spice Shampoo + Conditioner + Body Wash. I've seen that in the shower too many times. Why would you want to combine all of them together!?
I think that's what I use, shampoo/conditioner. Mostly because I don't pay close attention when shopping and just buy my usual brand of shampoo. I do almost no maintenance or styling on my hair, just a haircut every once in awhile and a basic shampooing in the shower to stay clean. Also, I could certainly be incorrect about this, but aren't most shampoos today usually just combined with conditioners? Perhaps this is more so for men?