Doctor Octopus' Tentacles
Dr. Octopus has possessed a total of three different harnesses during his career: the original titanium harness, a more powerful Adamantium harness, and the current harness, which was modified in 2004 to resemble the version seen in the movie Spider-Man 2. The original and Adamantium harnesses were both destroyed in the Lethal Foes of Spider-Man miniseries. The current harness has eight tentacles as opposed to four.
With his titanium harness, Doc Ock was able to beat Daredevil, a seasoned combatant with superhuman senses, almost to death out of sheer power. It was also temporarily worn by Spider-Man after Octavius' death, until the Hobgoblin caused it to short-circuit via pumpkin bomb. Spider-Man than proceeded to rip them apart when he lost control.
Using Adamantium Octavius created an entirely new indestructible harness, with all of the abilities he had before but with exponentially higher durability. Using this harness he was able to best Iron Man in combat, tearing the hero's armor apart with a defeat so harsh that Tony Stark began to doubt his abilities almost enough to resort back to alcoholism. He knocked the Hulk unconscious and, by Spider-Man's own reckoning, was "holding his own" against the combined forces of himself, the Hulk, the Fantastic Four, Deathlok, Ghost Rider, and Solo, even after the rest of the Sinister Six were defeated or fled.