The Coral Snake is probably the most easily identifiable venomous snake in AR. This is the pretty snake with the red, yellow and black bands. There is a harmless species of king snake which mimics this coloration (you might remember the poem "red on yellow kills a fellow"). I recommend leaving all snakes with similar coloration alone because these poems are easy to confuse and not always fool proof. Coral snake venom is highly neurotoxic, but the snakes are generally small and not prone to bite. They are rarely seen. They do not have the characteristic look of the boxy head with eye slits, like other venomous snakes in Arkansas.
The Timber Rattlesnake is becoming more and more rare because people normally kill rattlesnakes on sight. Adults can reach to 5 feet, but smaller snakes are more common. Timber Rattlesnake are a large-bodied snake with dark crossbands and a rust-colored stripe down the backbone. They are usually brown in coloration and they have a large rattle. Venom is highly toxic. They have vertical eye pupils and boxy heads.
Western Diamondback Rattlesnake
The Western Diamondback is the largest venomous snake in Arkansas. They are aggressive and have very potent venom. That's why I rank them as the most dangerous snake in Arkansas. The snake is easy to identify. First, look for a rattle. When threatened this snake will coil and make the typical rattlesnake sound. Second, look for the distinctive diamond pattern. The backbone of the snake has dark colored diamonds surrounded by white outlines. They also have vertical eye pupils and boxy heads.