Cleverbot
cleverbot.com
An early chatbot that learns from every conversation it's ever had, producing responses pulled from millions of past human exchanges.
Why it is useful
Cleverbot predates the current wave of AI chatbots by well over a decade, and its responses — pulled directly from things other humans have typed to it — have a genuinely strange, unpredictable character that modern LLM chatbots don't replicate.