Something I've enjoyed on occasion is a masturbation sleeve. They are soft rubbery sleeves with a small, stretchable hole down the middle. You lube it up with water based lube and use it over your penis. It feels really good, and in combination with some butt stimulation is a real mind blower. When I cum the semen comes drooling out the end, and is a little messy, but boy, does it feel good.
My son had three friends over last weekend. One of them had this plastic bag he kept trying to keep out of sight, so when they went out, I sneaked a peek into the bag to see what he had in there. To my great surprise he had two masturbation sleeves! He obviously intended them for group use, because first, he brought them to a sleepover, and two, he had more than one. One person can only use one at a time! The thought of them sharing a session with those sleeves was a real turn on. I noticed he took the bag with him when they went up to my son's room to go to bed, and the next day I checked, and they were wet inside from having been washed out. I'm really happy that my son is having fun like that. Like father, like son. When I was a boy I shared masturbation with friends, and enjoyed it tremendously.