I am almost hesitant to write this, as it seems these threads tend to cause controversy, but I wanted to offer my recommendation as I have used other posters recommendations several times before.
Having just got back from Santiago this morning, I wholeheartedly recommend Leonardo Cuzmar (firstname.lastname@example.org) as a tourguide in Chile. I used him for 2 things. First, kind of a random request, I asked him to get me tickets to the U de Chile v. Colo Colo football match, as I feared it might sell out. Leonardo bought exactly the tickets I wanted and personally delivered them to my hotel. He was very helpful. Second, my wife and I used his services for a day trip to hike in Banos Morales. I will keep this brief, but we were very pleased with his service. He is very friendly, answered all of our questions ranging from plants and birds to the history of Chilean politics. And, perhaps most importantly, I found him to be very flexible and courteous, his top priority seems to be making sure you enjoy your trip. My wife and I both agreed that our experience in Chile was made better by our time with Leo.
I won't go on any longer, so this doesn't seem like an infomercial, but if anyone has any questions about my experience, please do not hesitate to send me a message. I definitely recommend Leo for anyone planning a trip to Chile.