I was in Canada a few years ago. I first knew it would be a bad day when I asked for pancakes with original syrup, not Maple or anything, and the waitress sighed and said, "Can I just give you Maple? All the originals are unopened and I don't want to go in back and open one." I answered, "...no. I want original." I mean, you're going to have to open it eventually. Just do it. So she sighs really dramatically and takes the rest of my order. She doesn't bring me my drink before my meal, either. If it's busy, I can understand, but besides me, there were two other people. It was breakfast, and they weren't busy at all. What's more, I can see my plate sitting on the counter for a long time before she decides to pull herself away from talking with another waitress and bring it to me. I finished my milk, and she never returned (from talking to other employees, not even working on a table) to refill it. So when I left, I left her one penny, so she knew I was pissed off and didn't just forget to tip.
I know being a waitress sucks, so I'll tip even though they didn't give me much attention. But in this case, there was no excuse for such bad service.