So far we know you want a war theme on the Name, and the dude is in north america (presumable modern time?) Anything more you can tell us about him? Or more accurately, anything more about him you want the name to tell? Ethnicity, social standing, personality, etc?
As far as the ones you've listed:
Marcello->Has an Old World/Old Family/Old Money type of feel to it. Or a stereotype mafia, depending on the setting.
Marcus-> Too generic for a last name insofar as the war theme. Solid First Name.
Martin-> Same as Marcus
Kimball-> Opened you up for lots of Fugitive one armed man jokes, fair warning.
Callan-> Solid feeling. Not much immediate war vibe, or any other huge bias that I can think of. Vaguely makes me think of Hilghlander villains for some reason...
Kane-> Strong, but with the chaotic dark/haunted wanderer spin
Thane-> Similar to Kane, but with a more Law/Order feel. Has a historically feudal Scottish link (Personal favorite)
Ramm-> Gold, strong totemic name, without some of the cultural baggage of others.