Interesting. I never considered a scale of accents before. I just consider the word "nature," and I think: well, the first is definitely accented, so that makes two accented syllables in a row, thus a spondee. But nuance is everything! Such fun stuff.

And then this a few lines later: "Let it stamp wrinkles in her brow of youth." I hear a spondee in "stamp wrin..."

Just read this in King Lear: "Hear, Nature, hear! dear goddess, hear!" To my ear this starts off with a spondee.

...on an accurate depiction of people's lives as they are actually lived--this is a political act." --Philip Levine

I agree they're hard to come by. And it really depends on the delivery, but possibly knick knack? Hum drum?