Sebastian: I can't take much more testing.
Matt: I know how hard it is.
Sebastian: Bullshit. You don't know anything.
Matt: This isn't easy for any of us.
Sebastian: Fuck you, Matt! It is easy for you. I was to be in phase-shift for three days. It's been ten fucking days, all right? Ten days of tissue tests, radiation tests and your fucking needles! I can't fucking take it anymore.
Matt: What I meant was.
Sebastian: Fuck what you meant! And don't ever... Don't ever tell me how hard you have it.
Janice: What was the clientele like?
Frank: This guy comes up to me and he says: "l like my women like my coffee."
Janice: People still use that line?
Frank: Maybe he meant cold and bitter.
Janice: Very funny.
Linda: Let me tell you a little secret. The concept of Sebastian is much more appealing then Sebastian himself.
Sebastian: You know what, Matt? It's amazing what you can do... when you don't have to look at yourself in the mirror any more.
Carter: Oh, I'd suck the tits right off you.
Matt: My 5th grade teacher told me, that "Genius is the ability to go from A to D without having to go through B and C." Sebastian can do that, but for me, I gotta have the B and C.
Linda: Sebastian, do you have any idea what time it is?
Sebastian: Da Vinci never slept. Said it was a waste of time.
Suggested correction: Presumably the military are interested because Sebastian's research could lead to advanced forms of invisibility technology, such as the ability to turn materials and weapons invisible for use in combat.
You cannot second guess the film like that. Sebastian is making no effort to make non-living items invisible and throughout the film we see that is not possible (why else would Sebastian have to walk about naked?). His research is on animals (and later humans) not "materials and weapons" and is based on their physiology, anatomy and metabolism. How would you inject a rifle or a tank with a serum? They don't have a bloodstream. The military wouldn't see any value at all in this research - maybe they would be interested in invisibility, but not if it was restricted to living creatures as we see here.
You know how easy it would be for an invisible person to infiltrate an enemy's compound undetected and take out powerful leaders or dictators? Especially if no-one knew the technology existed.
Easy? Impossible. First, they would be naked and unarmed. Too bad if you are trying to knock off Vladimir Putin - a taekwondo black belt - with your bare hands during a Moscow winter! Being invisible doesn't mean you can avoid making a sound or triggering a pressure plate or an infrared detector and so on and so on. Final answer - a naked, unarmed combatant would be about as useful as a chocolate teapot in any form of operation, covert or otherwise.