My league got a dentist as a sponsor and we were able to get professionally made mouth guards for a nice discount and when I started wearing that guard, I thought it was the bees knees. Yet it was still fairly expensive, thick enough to make it difficult to understand me when I spoke, and still made me gag once in a while. That all changed when I went to RollerCon a couple years ago and found the SISU (formerly Protech Dent) mouthguard.
The SISU mouth guard is different from any other mouth guard on the market. It requires very hot water to mold to your mouth, it comes completely flat and has little holes in it, it comes in adult and youth sizes, and you can choose from 2 different thicknesses. There are spots in the middle that don't have holes where you put your teeth while forming the rest of the guard around your teeth with your tongue and upper lip. Once you have it in place, you suck until it's hard (hee hee). If you can flip the guard out with your tongue, you will need to do it again and suck harder. If you mess up, all you have to do is put it back in hot water to soften it up and do it all again. SISU has a great how-to video that helps first timers a lot.
Here are the pros and cons that I've experienced with the SISU 1.6 mouth guard over the past 2 years:
Some skaters have had an issue with the plastic taste of the mouth guards, fortunately SISU listened and created the FRESH flavor spray. Don't let the tiny bottle fool you, all you need is a tiny spritz from about a foot away and your mouth guard will smell and taste like peppermint for about 2 weeks. I didn't have an issue with how my mouth guard tasted, but now that I've tried the spray I'm hooked. The mint flavor isn't too sweet and I have a feeling my little bottle will last about a year, even with me going around spraying my teammates' mouth guards.