Some of famous oil painters that had signatures with distinctive features include Henri Matisse, Claude Monet, Leonardo Da Vinci and Pablo Picasso. Henri Matisse's signature varied, sometimes being fairly neat and at other times a quick scrawl. The "SS" in his last name remained larger than the other letters, no matter the style. Matisse even signed some of his work backwards, and the "SS" remained distinctive.
Claude Monet was known for his colorful landscapes and impressionistic style. His signatures remained much the same, except that he would match the color of the signature to the colors in his paintings. On some paintings he added the year the work was completed.
Leonardo Da Vinci was left-handed and had a habit of writing backwards. Like Matisse, his signatures sometimes showed up backwards on his paintings. No one is really sure why Da Vinci chose to write entire pages of text backwards. Suggestions include that he was trying to make his notes harder to read or that it was simply easier to keep the ink, or paint, from smearing when he wrote from left to right.
Pablo Picasso's most recognized signature is the underlined word "Picasso" with a large distinctive "P." The influential Cubist often didn't sign his work and sometimes got testy if asked to do so. After his death, it was left to his family to authenticate any unsigned work, which resulted in the creation of the Picasso Administration.