In no particular order:
1] Arrow - If their X project goes well, I foresee them doing very well in the future because X is only $11 million I believe, a pretty close figure to many custom inverts. And it's 200 feet high! It seems they have the're on the right track with a pretty low price.
2] Giovanola - From what I've heard they have a solid product that competes with B&M with a lower price. 'Nuff said.
3] Vekoma - It's been proven: while their coasters may not be that exciting to us enthusiasts, the GP loves them, plus they are cheap and they take up little space.
4] CCI - They have the ingenuity to keep themselves in business: great custom wooden coasters, competitive prices, and flexible techniques (aka Cornball Express, Hoosier Hurricane).
5]Intamin - Awesome, smooth coasters; great use of technology (magnetic brakes, anti-roll backs), and a large list of popular coasters.
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A New World. A New Technology.
One Last Hope for Salvation.
--Neon Genesis Evangelion