Buy that which you like, whatever catches your eye, and if you oval shaped glass coffee table cannot find something controversial, find something to put on it which will provoke discussion!
Glass is definitely good, particularly if you have an aquarium underneath. Metal can also be good, but it is advisable to be stainless for strength and corrosion-resistance.
Stay with exactly the same general style and colors of all of those other room. Fundamentally, if your furniture has dark woods, the...