Of all pavilions my favorite was Ontario House, located at Concord Place. Designed by Hariri Pontarini Architects of Toronto, this $4.65 million (design and construction only) building was by far the most inspired and striking. Its signature was the open air enclosure created with 42 km of cut white and blue rope chosen to evoke Niagara Falls. To hear one of the designers speak about the design, check out this link here. Apparently, kids loved the ropes!
The inner enclosed portion of the pavilion was functional, although had great content otherwise - technology, food, music, etc.