I once work on such a project..... Use gyros....
Or gyros with compensation of accelerometers...
Accelerometers alone WON'T help....
They are good at detecting rapid movement and such.....
And they will help you with reload buttons, secondary attacks like weapon kicks.... or even help you
switch weapons....
Don't use it as a mouse cause you are gonna have limited buttons and such....
Use it as a joystick..... It would be a hell more fun.... But also guess you gonna need a USB host for this
cause gameport quite doesn't even exists....
nowadays.....
Anyways.... I know gyros are hell more expensive and such.... But you are only gonna see good things with gyros....
Else you gonna waste time for nothing....
I wanted to make a hand mouse, so I really have looked some possibilities is it... But also may have overlooked others....
It's your choice.....
And hey..... Gyros are HARD to solder........ So either get a breakout board OR use RC gyros.... both are good!!!!