No sir, absolutely not, sorry, but no. 
Not sorry, actually—just no. 
Keep it simple, plain vanilla: nope. 
Not happening. Big en, big oh.

No way, no how. 
Negative, nuh-uh, ixnay, nyet. 
No no, no no. 
No-no-no-no-no-no-no.

Not likely, not likely. Maybe, 
but I doubt it. 
Possibly, conceivably, in theory. 
Uh-huh, mm-hmm . . .

Well, yeah, sure, O.K., why not, 
oh definitely, yes, 
wow, I mean anything, 
anything at all, when can we begin?