So basically just looking for expensive kits that are worth building?
The Special Hobby 1/72 CH-37 is definately different. Not the most attractive helicopter around but it is impressive and would definately add something unusual to your display case. Being a large limited run kit it can be a bit of a challenge to build. I know Sprue Brothers had it for around $50.
Zvesda's Mi-26 is also an impressive helicopter and much less fiddly to build than the CH-37. It is 1/72 but its a big helicopter (rotor span is about 18"). Its a nice kit, usually in the $45-50 range.
Trumpeters American LaFrance fire engine is a nice kit, and the ALF is a good looking truck. It is also the only plastic kit available of a modern American fire engine. It generally runs $60-80.
You can also have a look at the many Mach 2 kits, expensive, and usually have a rather poor fit, but for many subjects they are the only option. They offer some really neat subjects, just be warned many people say Mach 2 is the speed the model will travel when you throw it against a wall. In reality from the handful of their kits I have, I'd say you are getting early Airfix quality at current "Tamigawa" prices.
If you want to give resin a try Anigrand has some neat stuff, lots of experimental and prototype aircraft. I only have one of their kits, the Bell HSL-1, but it looks nice. Clean well cast resin parts. Not a highly detailed kit but not bad. I've heard some of their monster sized kits like the 1/72 C-17 have some problems due to the large castings.
http://www.anigrand.com/index.htm
If you are into armor Accurate Armor and Wespe models have some neat resin kits.
http://www.accurate-armour.com/
http://www.wespemodels.ro/