By far the best masturbator I have ever come across, the SlipInside #1|Slipinside #1 Nubbed Penis sleeve by Vibratex makes you want to cum just by inserting your penis.
It almost feels like silicone sliding over your penis and makes for mind-blowing orgasms.
The way to wear it is to insert your penis into the ticklers inside and then rub away. One thing I have done that no other sleeve has allowed me to do yet is to cum by rubbing the sides of the sleeve back and forth as if trying to start a fire with a stick by rotating it in the palms.
In fact, this sleeve feels better than a BJ or HJ. (Wait until you let your girl rub this up and down on your penis. You will melt and explode in rhythmic spasms, trust me.)

Cleaning is a breeze since you just have to turn it inside out and rinse off the ejaculation (which is held inside, a big plus in my book since no paper towels are needed to masturbate and catch it with.)
After the first few times you will become a pro at turning it inside out quickly and allow for some wonderful experiences

A standard vibe
SI = 5x better - A vibe is the only closest representation to the pleasure felt.

The tube love glove|Masturbation sleeves: The tube love glove
SI = 10x better and quieter

Carmen's tight ass|Pocket pussies: Carmen's tight ass
SI = 20x better (As as well as softer, and easier to manage, in fact this even feels tighter than that. The "Futurotic" seems to stretch a lot and attract a lot of crap, as well as hold water)

2-tone anal masturbator|Pocket pussies: 2-tone anal masturbator
SI = 30x better (compared to SI, I could do better probably with a damn ziplock bag! haha)

Vroom = 5 / Bee = 2

for loudness (or more like quietness) of the lube being rubbed around on the inside. (It can easily be drowned out by music)

One other thing everyone should try: Get some olive oil, and take it in the shower. (The olive oil allows it to stay slippery, unlike the water just breaking down the water based lubes creating the only lube as water, which = too much friction) It appears to be perfectly stable with water based lube|Maximus water based lube and olive oil. (have had a chance to try it yet with silicone, but I am sure it should work with that too.)
For me personally, this with the aid of a g-spot vibe (but used anally) has allowed me to cum in the shower for the very first time! Quite an accomplishment, if you ask me.

I just wish I could find another sleeve that feels this good. I am still on the hunt for that and will let you know if I find one.