Death-lock pincer

Megatron prefers to get up close and personal when he encounters a target. Often, he will use his death-lock pincer to attack an opponent. Wielding a crushing force range of 576 psi, it also possess a telescoping blade that has a burn rate of three kilojoules per second.

And it that wasn't bad enough, Megatron can also access his fusion cannon while using it. It will thoroughly ruin your day if you come across it.

Fiction

Revenge of the Fallen movie

During his battle with Optimus Prime over Sam Witwicky, Megatron extended the death-lock pincer for his battle with the last Prime, but Optimus countered by unsheathing his own Energon Sword and laid the smack down on the Lord High Protector. When Starscream and Grindor arrived, Megatron sheathed the blade, but popped it back out while talking about whether or not Sam was worth the future of the Cybertronian race, making the fleshling a little panicky. However, when Optimus turned his back after killing Grindor, Megatron impaled Optimus from behind with the blade on the pincer. Just to make sure the job was done, Megatron then fired a blast from his fusion cannon, extinguishing Optimus Prime's spark.

Later, after he was revived and received parts from Jetfire, Optimus attempted to kill The Fallen and avenge his lineage. Megatron came to his master's aid by slashing Optimus with his death-lock pincher...and Optimus countered by breaking the blade in half with his bare hands! To top that off, he then forced Megatron to eat a blast from his own fusion cannon in the face, then sliced off the arm. Revenge of the Fallen

Notes

• 600 psi actually is pretty damn wimpy. A pro boxer can deliver a 1300 psi 3-inch punch. So 600 psi probably couldn't kill you.
• The figure for his "burn rate" is slightly more convincing - 300kJ/sec is 300 kW, on the order of 400 horsepower.