Switzerland and Germany have been my worst experience with Austria coming in a close 3rd (German speaking people mean?...nahh don't wanna go there).

Canadian officers, at least the ones in Quebec at the isolated crossing are no picnic. In college I used to go back and forth over the border all the time. Coming back from Vermont with girlfriend and 2 friends was one that sticks out most:

Officer: Citizenship?
Me: US
My passengers: Canadian, US, Canadian
Officer: Anything to declare?
Me: Nothing
Officer: Are you sure
Me: Yes we didn't buy anything, just went Jay to ski for the day (there are 4 pairs of skis on top of the car, we're all wearing ski pants, so I'm really just stating the obvious)
Officer: So you went to ski and didn't buy anything else?
Me: Yes, just skiing
Officer asking my friend: And you're sure you have nothing to declare?
Wise ... friend: Nothing but my undying love for my country mam.
Officer: Very original, haven't heard that one before. Pull over please.

It was about 10 below we were all exhausted after skiing all day and had to stand outside while she and her pal inspected the car for about 45 minutes including opening up the ski bags, inspecting boots, just a nightmare. I was praying someone hadn't bought a postcard or something, cuz they would have probably fined us for smuggling undeclared goods and seized the car.
There was a 0.0001% that we had anything to hide, she knew it, but she were bored, we pissed her off and spent 45 minutes freezing as punishment.

On the other hand the US dudes were were pretty cool
Crossing into US for a Taco Bell run (no TBs in Quebec, closest one in Plattsburgh, NY about 45 miles away)

Officer: Purpose of visit to US?
Friend who is driving: Going to Plattsburgh
Officer: What for
Friend: Taco Bell
Officer: Making a run for the border huh?. Smiles, waves us through.