B_Steele
Mongoose
I'm sure what they actually trademarked was a very specific use of the word.
As a huge comic geek as well as a gamer, I must chime in.
Marvel did not trademark Death...they trademarked the use of the term in relation to an image they had drawn for a character. Essentially, no one could draw the same character in a different media and title it Death. It's like Wolverine. You can't trademark the explicit use of the animal's name, but if you attached it to a hairy guy with claws on his hands that said 'Bub' way too much...Quesada would soon be sending in the Legal X-Team.

Again, context is big in these sorts of legal situations.
-Bry