Linwarrior 3D... not bad but not amazing.
1) implies Linux only
2) not-so-subtle reference to another franchise of the same genre, but the context does not carry over ("warrior" is ambiguous)
Could there be a better name for the game?
Starting points:
1) hc: how attached are you to the "Linwarrior" brand?
2) is there risk to using the key term for getting brand recognition: "mech"?
Is it trademarked? Short answer: yes. Long answer: not in a way that prevents its use. Two companies hold trademarks on the isolated term "mech" and neither are relevant to computer games. One is a plumbing supplies company, the other is the military.
Here's a (tame) suggestion, as an example that could be used: Mech Frontier