The story goes that Marvel architect Stan Lee was racking his brains trying to come up with a new hero to capitalise on the success of his earlier heroes when he saw a spider crawling up his wall.
That mixed with his desire to create a teenaged superhero who would appeal to his principal audience and produced Peter Parker, the Spectacular Spider-Man, one of the company's most famous creations!
Totally a rip-off of: The Spider Queen
A famous creation that was remarkably like an early one, natch. A good two decades before Spidey swung onto the scene Shannon Kane was fighting crime with the help of special web fluid that she fired from a bracelet with the flick of her wrist. The Spider Queen was motivated by a similarly tragic backstory as Petey and his Uncle Ben, having lost her lab assistant husband to some nasty so-and-sos.
Taking his invention of web shooters, Kane dedicated herself to fighting crime! She may not have had Spider Sense, increased strength or a snazzy costume, but the web shooter gimmick is weirdly close to Spidey's. Lee has also admitted to being influenced by old pulp stories and comics when coming up with the wall-crawler, so it's not outside the realms of possibility.