Well I'll chip in with the Habs players.
I can't believe no one mentioned Stephane Richer yet. Still has 2-50 goal seasons. In Montreal, that should have ensured he has a longer career in Montreal, but all that talent (stickhandling, skating, shot, size) was not enough for him to want it every night. Was tough enough too. I still remember him pummelling Milbury in the playoffs after Milbury jumped him. Mario Tremblay who was commenting, called it a typical Milbury tactic to jump a defenseless rookie. I always said that the best line he played on was with Skrudland as center and Corson as left winger. Not the Bobby Smiths, and Mats Nalunds type where they control the play. I also always maintain that Richer was traded against his ideal center in Kirk Muller. Muller played a lot like Skrudland, except much more talented, better skater, shooter and passer. I would have loved to see a line of Richer-Muller-Corson. Good size, strength, talent. They could all go in the dirty areas and could beat you on the rush.
Ryan Walter was briefly mentionned, and I believe he belongs on this list. The 2nd overall pick (77 I believe) behind Bobby Smith. In his early career in Washington, he was a very good tough offensive player. Not that he had a bad career in Montreal, he was a realiable 2nd/3rd liner mostly. But he did run into injury problems also.
Russ Courtnall - He had a few good seasons, but irregardless, he always left you wanting more. No one could skate as fast to get nowhere it seems.
Gary Leeman - Good years in Toronto. A perenial 30 goal man until he hit 50 in a career year, then he gave us the Wayne Babych treatment. At least he got his cup in his short stint in Montreal.
Gilbert Dionne - A lot was expected from him when he came up to Montreal for half a season, scored 20 goals and made the All-Rookie Team. But he gave you the feeling that he was a jealous, selfish player with a sense of accomplishment. The most lasting memory of him is the 93 playoffs, in OT (forget the opponent), apparently the puck deflected off his chest from a shot from rookie Brisebois. Everyone jumped Breezy, but Dionne was there pointing at his own chest, screaming "it's me, it's me". Anyways, he didn't last all that long after he was traded.
Murray Wilson - I don't remember Murray too much, as I was a kid and Murray played the 4th line. But he was fast and could score 20 goals from the 4th line. You'd think a guy like that could give you more, if you would just ask.
Kjell Dahlin - What can I say. Came into the league in 85-86. Part of the 10 rookies that Montreal marched to the Stanley Cup in the spring. Was scoring goals and points for Montreal for about half a season but did not like getting hit. Was afraid of his own shadow. Had a hard time getting in the lineup at the end of the season and playoff due to wide yellow streak down his back. But he still finished atop of the rookie scoring list that year.
Oh I almost forgot to add the name of Lafleur as previously mentionned here. It just could have been more than what it was already, his career. He proved he could come back after 3 years, although not at the same level, it was still respectful. If this guy would have taken better care of himself instead of living the disco lifestyle, he could have done more.