Probably the first set I ever decided to chase hard and fast was the first variation of these Expo cards.  Available as incentives for buying/opening boxes or cases at the annual Spring and Fall Expo, one year they decided to have a portion of the set dedicated to Team Canda players, and as it was more rookie focussed that meant World Juniors which is my absolute favorite thing in hockey every year.  That Expo I made a point of visiting every table regularly hunting for these as they popped up.  I continued to do that most years and really enjoyed the chase.  The addition of very shortprinted superstars as case break incentives soured this a little, but I did manage to get quite a few.  If you've got one that I don't have here, please do let me know.