I've seen the oddest things in Eugene...
multiple unwrapped condoms (the way they're wrapped, I assume when they're unwrapped, they're used...) all over campus
bumcamps (sleeping bags laid out, but no one home)
shopping carts in the Millrace (a new one every year)
random car accidents

In Hillsboro, it's pretty much limited to
People who aren't home letting their dogs loose
novelty roadkill
yuppies sans helmets
poor folks sans helmets
(ever notice how it's either the yuppies who are 'too cool' for head sweat/helmet head, or the poor/homeless people on walmart bikes (or possibly stolen bikes) who never wear helmets? Do they ever look at each other and then at the helmet-donning community and 'get it'?)
Groundscores (t-shirts, etc that I throw in my bag and wash the heck out of when I get home)
.... uh... that's it. =P