I know just a tad about this trademark deal since I've personally applied for one.
Looking at the USPTO trademark database, the only entry for a trademark for "Millenium Force" is for Cedar Point. They've registered it as a trademark under the following categories (forgive the caps, I'm cut-and-pasting directly from the site:
International Class 006
Goods and Services KEY RINGS
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International Class 008
Goods and Services TABLEWARE
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International Class 016
Goods and Services STATIONARY, MEMO PADS, PLAYING CARDS, POSTCARDS, WRITING UTENSILS, PAPER PENNANTS
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International Class 018
Goods and Services UMBRELLAS, BAGS, BACK PACKS, FANNY PACKS, PURSES, WALLETS
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International Class 021
Goods and Services KEY RINGS (NON-METAL) (Int Cl 20); MUGS, PLATES, BEVERAGEWARE, SOUVENIR GLASSWARE
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International Class 024
Goods and Services PENNANTS, TOWELS
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International Class 025
Goods and Services CLOTHING, NAMELY, JACKETS, T-SHIRTS, CAPS, SWEATSHIRTS, TANK TOPS, HATS
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International Class 026
Goods and Services ORNAMENTAL NOVELTY PINS
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International Class 028
Goods and Services TOYS, GENERAL NOVELTY ?? ???????? ?????? ????????? ???? ???? ????? ?????????????????????????????????????????????????????????????????????????????????????????? ?????????????????? ????? ?? ?????????? ??? ???????? ????????? ???? ???????? ????? ?????????????????????????????????????????????????????????????????????????????????????????? ?????????????????? ????? ? ?????????? ??? ???????? ??? ????? ??????????? ????????????????? ???????????? ???? ???? ????? ?? ???? ??? ????? ??????? ????? ????? ????????? ??? ???? ?????????? ????? ????? ??? ?????????? ???????? ???? ??? ????? ??? ????? ??????? ? ?????????? ?? ???? ????? ???? ?? ??? ?????? ?? ???? ?? ???? ??????? ??? ??????????? ????? ?????????? ????????? ??? ????????? ???? ??? ????? ?????? ?? ???? ?? ??????? ? ?? ?? ????????????????? ??????? ??? ??? ?? ????????? ??? ???? ?????? ??? ?? ????? ?? ????? ??????? ???? ????? ???????? ??????????????????????????????????????????????? ??????????????????????????????????????????? ??? ???? ??? ???? ????? ???? ?????????????