Absolutely nothing graphic. Some dead animals are shown but no gore. Lots of mild slapstick violence in almost every episode all of which is played for comedy.
Skipper sometimes takes off his captain's hat and smacks Gilligan on the head with it.
In one episode, the show parodies the short story "The Most Dangerous Game". A big game hunter comes to the island, takes the castaways hostage, and tries to hunt Gilligan. Several shots are fired in the episode, but needless to say no one is ever hit or killed.