This thread contains the wisdom I've gained over the years. I've been RP'ing for many years, and I've made a lot of mistakes. I give you this advice so that you might learn from those mistakes. Following these guidelines will help more people want to RP with you, and help you have more fun.
Elemental Benders, Magic Users, Power Rings, Telekinetics
Do not grab an enemy. Holding someone floating in the air with all of their limbs held firmly by your vice-like telekinetic grip is not fun. Remember, your opponent should always have some way to retaliate and defend themselves. You also shouldn’t tie your opponent in rope, chains, tendrils, or swarms of honey bees. You wouldn’t like it to you. Reaching for them with such a tool, with the plan to slam them around once or twice before letting go, is just fine. That gives them the option to either dodge the grab or just bear through the punishment. Either way, they can actually do something on their next turn.
Tanks
Don’t breeze off everything. Even if something wouldn’t do any real damage to your character, it’s nice to make your opponent feel that their attack counted for something. Validating their attacks with a reaction from your character will make your opponents feel appreciated. Maybe they punched your nearly invincible character in the face. Instead of laughing it off, however, you could have the force of the punch knock you out a three story window, knocking the wind out of your lungs. Perhaps you could stand up afterwards and glare up at your foe, realizing you may have underestimated them.
Speedsters
We get it, you’re fast. But nobody is going to want to fight your speedster if they just evade every single attack. On a role playing site with an emphasis on combat, that can be deadlier than the very lasers your character is dodging. So get hit. It doesn’t have to be getting impaled through the heart. Maybe jumping over an attack makes you miss your step, sending you tumbling. Make your character suffer their defeats and work for their victories. By suffering at least little injuries, you will satisfy your opponent’s blood lust.
Robots
Don’t play a robot. If you must play a robot, give them a personality. Find a way to give them emotions, quirks, likes, dislikes, and goals. Playing a static character is just not fun. Role playing is about forming and constantly changing relationships with other characters. If your character has nothing to contribute and nothing to gain, then you’ll always be alone, even in a room full of people.