The weirdest ones for me are ads for lumber. Like, I go to the local lumber yard website to check dimensions of what types of lumber is available when I'm planning a project. That lumber is typically costing $1-$2 per yard, so I frequently only buy lumber for ~$20, and they'll show me ads at least ten times. Their ROI has to be very low?

Adding insult to injury, I only buy lumber from their competitor, who, although having a sucky website where I can't look up dimensions, will let me use their compound mitre saw for free, saving me a $600-$1000 purchase.