Not necessarily for endurance competitions (I know Arabians are a popular breed for that), and I know any horse can be a great trail horse despite the breed.
But what breed of horse did you have that was the best/most fun/most brave/handy/whatever trail horse? Just for a fun topic.
Mine has been my 12.3 hand stocky Welsh cross pony. He has solid hooves, is quick and responsive but will walk on a loose rein, loves to lead but will follow too, goes anywhere you point him, and is extremely handy and brave. I adore him.