I could think of three for the Rangers.
1. The Pavel Bure deal in 2002. Bure for essentially a first round pick, being that Ivan Koltsov and Filip Novak still haven't seen NHL action
2. The Alexei Kovalev deal in 2003. Kovalev, LaCouture, Wilson and someone else for Fata, Lintner, Bouchard, and McKenna. Wow talk about about bad, even for a salary dump.
3. Jagr and half of his salary eaten by Washington for Anson Carter, straight up. My all time favorite. It's COMPLETELY backfired for Washington, not only are they still paying him over 4 million a year, but he just had one of the best seasons of his career for the Rangers, and Carter was then traded at the deadline for Jared Aulin, who still has not lived up to any potential he ever had.
I'll give three bad ones as well where the Rangers got fleeced...
1. The 96 Deadline Disaster. Ferraro, Lafayette, Norstrom, and Steve Larouche for McSorley, Kurri, and Churla. Killed any momentum we had as a team, and killed us in the playoffs. All 4 of those players we got were USELESS for us. Ferraro went on to have some good seasons elsewhere, and Norstrom became one of the league's best stay at home defenders. We got KILLED in this trade in hindsight.
2. Zubov and Nedved for Robitaille and Samuelsson. How do you trade a point per game defenseman who lead your team in scoring the season before for a guy who was just seperated from Gretzky, and wasn't scoring a whole lot anymore, and a defensive defenseman? Nevermind Nedved, I could have dealt without him, Messier was right about him the first time around, too soft, didn't work hard enough. Thank god the Pens then fleeced themselves and he ended up in Dallas.
3. Middleton for Hodge. The worst Ranger trade ever. Why? Because Middleton was still blooming, and had a world of potential, and Hodge, I thought, was an overrated player who got his points from playing with a great Boston offense that consisted of Esposito, Bucyk, Sanderson, Cashman, and Orr. Hodge had one ok season with the Rangers and did squat after that. Middleton went on to score over 400 goals and almost 1000 points. Not only that, but Middleton was 21, and Hodge was 32, we lost 11 years in that trade.