Around here, the trash company charges you to pick up trash, but curbside recycling is free. Of course, they don't inspect your recycling before they dump it in the truck, so if you wanted to you could just pay for the smallest available trash can and put the rest of your trash in the recycling bin.
What about parking outside the gate of parks? California State Parks charge for parking, not for admission, so there's always a crowd of people parked just outside the gate along the road, saving $10 by not parking inside the park, even though they just walk in and use the park's facilities anyway.
Or the always popular telling your kids to lie and say they're under 10/12/whatever-age-gets-a-discount to get into places. My parents used to do this to me when I was 12 and 13, they'd tell me to say I was 11 to get reduced admission to places. I *HATED* it, not just because they were telling me to lie, but because I was self-conscious about being small for my age and they were drawing attention to this to save a few bucks.
I seem to see a whole slew of Starbucks exploits that people do to save a few cents, like ordering a small drink with "no room" in a medium-sized cup, and then filling it up with cream and sugar, instead of ordering a medium drink with room for more money. The employees never seem to care enough to fight it.
I don't think that violating contracts is necessarily unethical, since so many are predatory. This is especially true to me for contracts that are wholly one-sided that you never actually sign, like software license agreements or anything like, "by using [product] you agree to [ridiculous terms]".