I've read these technique postings with interest and I'm surprised to NOT see one that I've been using for about 2 years now that I actually learned from the internet. I would especially like to suggest it to the guy who uses grapefruit and cantaloupe because there is something much much better: plantains. A plantain looks very much like a banana only larger and the skin of a green or just ripe one is much thicker. In order to do this, you need one that's just ripe, not too ripe, and green won't work. It should be yellow with a minimum of brown or black on it.
Cut the tip of the plantain off about 1 inch from the end (usually the end where it connected to the tree, because it's wider at that end) and starting at place where you cut, begin squeezing out the firm/mushy contents like toothpaste out of a tube, working your way up and squeezing out all that you can so that you are left with an empty sheath that should fit over a typical sized penis. What to do next should be obvious: insert your member in the thing and massage yourself with it. Optionally, you can add a little lube to the inside, though typically it wont need it as the squishy plantain pulp works as lubricant, but I like to add a little 'hot' lube for extra sensations. For the best results, when you're at the supermarket, select plantains that are big enough around to accommodate you. I actually stand at the bin picking them up and measuring them by gripping my hand around them like a cock and discarding the ones on which my middle finger can touch my thumb. If you can keep the plantain intact (no splitting) while you jack with it, so that it forms a partial vacuum around your erection, you'll find it even more pleasurable. To do this, you'll have to carefully squeeze out air as you put your dick in it.
When I first read about this technique I was really intrigued and rushed out to buy some plantains in order to try it and I've been addicted to this method ever since. I was really surprised I'd never thought of it before myself as I've always been on the lookout for new masturbation techniques and toys and I'd been masturbating heavily for 30 years before I'd found this. I guess the main reason is that I had never purchased plantains to eat before: they have no real nutritional value, have to be cooked in order to be eaten, and I don't find them that tasty. (You've probably had them cooked with cinnamon and sugar as a side dish if you've eaten at Cuban restaurants). In fact, it's hard to think of them for any other purpose, they're much cheaper than grapefruit or melon and I don't feel like I'm wasting food. (Well, maybe you actually eat the melons or grapefruit after you make love to them, that's cool).
I'm a gay man, so I've had the opportunity to introduce this technique to a lot of guys and most of them have found it very pleasurable. Some guys are extremely thick-dicked and will split almost any plantain skin you try and put on them, but even without the vacuum effect, the soft slippery wrap-around feel of a plantain skin can still provide a breathtaking wank.