Elastic Touch
Jam can turn anything he is touching into a bouncy substance, like elastic. The radius for this technique is around double his height. If Jam cancels this ability while an object is bending, it will stay in that position and return to its previous state. (e.g. if he bends stone, it will stay bent, but if he bends water, it will start to flow.)

Weapons Mastery
Jam can wield all sorts of weapons with the skill of a master, but he needs them custom-made and can only take one into each battle.

Weapon Manufacture/Seals Mastery
Jam has extended the art of seal tags, welding them into all of his customized weapons. He can make weapons do things like melt on impact or shoot lasers. This art also allows him to keep a weapon in Hammerspace (behind his back).

Pseudo-Random Fighting Style
Jam can seamlessly switch between fighting styles, using momentum and confusion to make up for his worse than average bone consistency.

Overcharge
Jam can overcharge his muscles for a brief period. During these instances, he can punch through blocks of Minecraft-imported obsidian. The range of his elastic powers also increases to several miles.

Elastic Touch
Jam's Elastic touch only works up to twice his height in any direction from the point he is touching, and he can't use this ability on anything living.

Suits of armor, however...

Brittle Bones
Jam has fragile bones, and generally breaks a bone or two per battle. His unique fighting style and many of his abilities actually began as ways to combat this deficiency.

Weapons
Jam can only carry one large weapon or several small ones in Hammerspace at a time, and having a heavy weapon outside of Hammerspace will drastically slow him down.

Seals
Although Jam is proficient in seal tags, his undertested experiments are often unstable and liable to forceful backlash (read: explosions) under strenuous circumstances. The more he tests a weapon, the more refined and stable he can make it, but the greater the effect, the longer this process takes.
A list of stable and unstable weapons can be found below.

Overcharge
Jam's overcharge is a last-ditch attack, as it will shatter every single bone in his body if he hits anything even mildly solid.

NOTE: All heavy weapons have seals to make them light enough for Jam to carry. All unstable weapons can be willingly exploded by Jam at any point, even from a distance.

Stable
Ball 'o Bounce- Just a ball on a rope. Jam uses his elastic powers on the string to make it stretch, and the ball to make it bounce. Heavy.

Snap-Shield- A gigantic square shield. Jam uses his elastic powers to turn the shield into a sort of trampoline which can rebound most projectiles. Fire- and explosion-proof. Heavy.

Unstable
HammerSpace/Time- More like a metal mallet. Both ends shoot jet flames, activated by buttons on the handle, for propulsion. Liable to explode if the 'jets' are overused, or if the head is pulled off the handle. Heavy.

Jam was born with a natural calcium deficiency, and until the age of 15, he was unable to take part in any sports. Predictably, he managed to get it into his head that he would eventually become a great sportsman, and set out to research the possibility of superpowers.

Jam's month-long journey led him to a lake in some woods, surrounded by mountains that he had somehow failed to notice before that point. His attention was drawn to a dim light in the sky, which slowly grew brighter until it burned to look at.

His last thought before the flames engulfed him was 'This is cliched.'

Jam awoke back at his home, and shrugged the entire ordeal off as a month-long dream, setting out in a different direction this time, just to be safe. He slept through the gigantic fireball that ravaged the countryside.

This continued until Jam finally figured out what was happening: he was looping in time, and had one month to stop the meteor from hitting his country or he'd have to do it all over again. He began researching various weapons and techniques, but nothing would budge the meteor. Despite his moronic tenacity, he eventually gave up and spent his remaining month with his ten-year-old brother.

On the final day before the meteor was due to strike, Jam's brother found a small rock, and began bouncing it on a kiddie trampoline, playing keep-ups. Jam was struck by an idea and rushed towards the lake, remembering a martial arts exercise he had once done, using a body of water to stand on.

Determined to save his family and friends this time around but lacking the time, Jam barely noticed the speed he was running, and didn't register the snaps of his bones. Finally, several miles from the lake, he slammed his fists into the ground, the landscape seeming to sag just as the meteor collided in the distance. Jam closed his eyes in despair, awaiting the final judgement from the rock.

Needless to say, he was surprised when the floor bounced back, pinging him exceedingly close to orbit.

And thus began the legacy of Jam Usagi. (Yes, that's his surname.)