Rising stem gate valve
The most common type. Has a threaded stem that rises up and down to open and close the valve. Often used for isolation and throttling applications.
Non-rising stem gate valve
Has a stem that does not rise, only rotates. The gate travels up and down the stem threads to open and close. More compact but can be more difficult to determine if the valve is open or closed. Used for the same applications as rising stem valves.
Wedge gate valve
Has a tapered gate that sits in a tapered valve body seat. As the gate closes, it is wedged into the seat for a tight shutoff. Typically only suited for on/off applications.
Knife gate valve
Uses a gate with a sharp bottom edge to cut through solids like slurries. The gate slides through slots in the valve body. Commonly used in pulp and paper, waste and water treatment applications.
Double disc gate valve
Has two parallel discs in the flow stream instead of a single gate. The discs squeeze together to shut off flow. The discs are less likely to jam when closing which can allow tighter shutoff. Used for severe service applications.
Flexible wedge gate valve
Uses a flexible wedge gate, typically made of rubber. The wedge conforms to the pipe shape for an optimal seal. Resists material buildup and used for slurry applications.
Split body gate valve
The valve body splits into two halves, with the sealing surface between the halves. The gate is contained within the bottom half. This allows the top half to be removed for gate access/maintenance without removing the valve from the pipeline.
There are a few other specialized types of gate valves as well for high temperature, cryogenic and other applications. But the ones gate valve factory listed above are the most common standard types of gate valves used in piping systems.