Grim Fandango is the only one I've played, and it's awesome! 

I can tell you for a fact Battlezone is actually a pretty decent game.  One of the best to blend action and strategy together, specially when you consider it was made 12 years ago.

+1 for playing Grim Fandango. It's hard though, and it's uber-buggy, so plan to spend lots of time with emulation config files.

Dude get on grim fandango and warhammer 40000 cause they both are awesome.

I'm playing through Freedom Force for the 3rd time now. I love that game. The characters and the writing have just the right mix of reverence and humor. Its probably the shortest of all the games on your list too so you should really check it out.

On this list I've only played The Witcher which I wholeheartedly recommend. Great game. 

Arcanum is rightfully at the top of your list! Dave isn't driving you crazy about this??

I have yet to play a single one of those. :(

You should really check out Grim Fandango.  It shows what we're missing when we think the adventure game genre is dead.