I'll second Lamarca on that line - great. Not read that for ages.

Others:-

"Only you can save mankind. If not you, who else?" Terry Pratchett (a _very_ good book written at the time of the Gulf War, and extremely appropriate now)

"When a day you know for a fact is Wednesday starts off by sounding more like Sunday, something is very wrong." Day of the Triffids, John Wyndham

"I can't get used to the fact that I can kill my friends just by pressing my tongue against my back teeth in a particular way. So I tend not to have many friends." Daughter of Regals and other stories - Stephen Donaldson

Read any Neal Stephenson, and I can find a dozen favourite lines without hardly looking. But the one that sticks around, for the efficiency and nerve of it, is:-
"After that, it was just a chase scene."
Snow Crash - Neal Stephenson

Graham.