Oregon Tiger

I think it originally came from a famous scene in "Animal House"

D-Day: War's over, man. Wormer dropped the big one.
Bluto: Over? Did you say "over"? Nothing is over until we decide it is! Was it over when the Germans bombed Pearl Harbor? Hell no!
Otter: Germans?
Boon: Forget it, he's rolling.
Bluto: And it ain't over now. 'Cause when the goin' gets tough...
[thinks hard]
Bluto: the tough get goin'! Who's with me? Let's go!
[runs out, alone; then returns]
Bluto: What the frick happened to the Delta I used to know? Where's the spirit? Where's the guts, huh? This could be the greatest night of our lives, but you're gonna let it be the worst. "Ooh, we're afraid to go with you Bluto, we might get in trouble." Well just kiss my arse from now on! Not me! I'm not gonna take this. Wormer, he's a dead man! Marmalard, dead! Niedermeyer...
Otter: Dead! Bluto's right. Psychotic, but absolutely right. We gotta take these bastards. Now we could do it with conventional weapons that could take years and cost millions of lives. No, I think we have to go all out. I think that this situation absolutely requires a really futile and stupid gesture be done on somebody's part.
Bluto: We're just the guys to do it.
D-Day: Let's do it.
Bluto: *Let’s do it*!