I cant think of any real rebels at the moment... except Maeglin-Eol and the whole family of Tar-Palantír.
About the first one: Aredhel, the White Lady of Gondolin and sister to Turgon king of the Gondolindrim, fled her city and in the wild forests met Eol the Darkelf who lived alone in the forests and took her to be his wife. They had a son, Maeglin (or Lómion, as his mother called him); his father told him everything about metals and forging as he was a smith, but his mother Aredhel always told him stories about the glorious elven warriors of Gondolin, and so some day she persuaded him to leave Eol. With the stolen sword Anguirel he fled to Gondolin, where he won a lot of glory because he knew a lot about metals; but his father had followed them, and he was so angry about his son that he wanted to kill him with a spear, but his wife Aredhel stepped between them and so she was killed. After rebellion against the king and his son who spoke against him, he was killed by the men of the king, thrown off the rock of Caragdûr. In his last words he cursed Maeglin and spoke a ban than Maeglin should one day die the same way as he did, and indeed after Maeglin had treated the city and told Melkor how to defeat the Gondolindrim, he was killed by falling off Caragdûr.
The other one takes place in the dark years where Saurons shadow lay over Númenor, and the King's Men were against the Elves; in these days Tar-palantír became king, and he was totally different form his father who had forbidden any contact with the elves, but Palantír was one of the elvellyn, the elf-friends, like his mother Inzilbêth, and his father also wanted Palantírs brother Gimilkhâd to become the next king. Palantír had many enemies, among them his brother Gimilkhâd and his nephew Pharazôn (who finally wedded Palantírs daughter Tar-Míriel).