Spyro 2: Ripto's Rage and Spyro: The Year of the Dragon. There's an easy glitch in both of these games involving water. Whenever the water is even with land this glitch is possible. The levels that I've had success with doing this is Breeze Harbor in Spyro 2 and Bamboo Terrace in Spyro 3.
In Breeze Harbor after you heat the machine in an area, the water will rise and even with one of the steps. When you have Spyro in the water and swim to the very edge of the step, press square to go underwater and move Spyro forward. He'll dive underwater OVER the water. So what is usually air is now water and you're free to roam wherever. Be warned that this glitch will cause the game to slow down significantly, especially if you swim toward the "end of the sky" or try cheating by picking up all the gears that you're supposed to use the trolley for. Also, since you're "underwater" you can only defeat enemies by charging, so it would be in your best interest to defeat enemies that you can only flame beforehand. In order to exit the glitch, try diving back into the water, falling off the edge of cliffs, mounting machines (such as cannons or flying boats) or sometimes talking to other characters will ground you.
Doing the same glitch in Bamboo Terrace is much more difficult. If you do this one incorrectly, you'll fall over the edge of the waterfall. There are several small water areas in Bamboo Terrace, but the one you'll need to find is toward the end of the level before the final pagoda. The waterfall has a few raised platforms that will lead you to the other side. Clearing the area of the enemies first is a good idea, since they use projectile weapons. When you have Spyro in the water, swim almost to the very edge. Use the same method as in Breeze Harbor, but you have to do it much more quickly. Another way you can exit here is by entering a side quest portal.
Spyro 2: Ripto's Rage Summer Forest water glitch. This glitch is almost opposite of the previous two glitches (and is really hard to explain). Be sure to save your game before you perform this because there is no way out. This glitch will be much more easy if you've already completed the game and have the superflame ability. In the area containing the portal to Glimmer there is a small pond with a hidden underground tunnel. Take it to the small room with steps. This is the room that contains an orb at the top of the steps. It also leads outward to the large area with the pond where you first learned how to swim, the jumping and flying tutorial with Hunter, and levels Idol Springs and Colossus. When you're at the top of the platform turn Spyro left toward the outer wall with bright green grass. If you have the superflame ability flame at this wall until you find the place where you're flame doesn't make contact. Instead, it should go through the wall. If you don't have the ability, you're just going to have to guess. Now, you're going to fly but do not hover, you still need to continue flight after you're through the wall. Once you're outside of the Summer Forest boundary start flying right. You want Spyro to fly underwater and you should be able to see through the wall. Spyro will continue flying even though you positioned him underwater. You can walk all over the floor once you've landed, but since the water is fairly deep you will have to restart the console in order to exit the glitch. There isn't as much gain to this glitch as the previous ones, it's just interesting to try.