It's important to remember that food webs are complex and vary depending on the ecosystem. Here are two examples of organisms often found at the top of food webs:

* Apex Predators in Terrestrial Ecosystems: Wolves are an example of an apex predator in many forest ecosystems. They sit at the top of the food chain, preying on deer, elk, and other large mammals.

* Apex Predators in Marine Ecosystems: Great White Sharks are a classic example of an apex predator in ocean ecosystems. They sit at the top of the food chain, preying on seals, dolphins, and other large marine animals.

Important Note: The concept of a single "top" of the food web is sometimes oversimplified. Food webs are complex networks with interconnected relationships. There can be multiple apex predators within an ecosystem, and some organisms might even be considered apex predators in one area but prey in another.