I prefer big box trucks. You can draft a long ways back and still get the benefits. I'd be afraid to draft any sort of construction truck because of the aforementioned risk of getting hit with rocks. I've had a windshield broken that way. (Not drafting, just happened to be passing one on the highway.)

In all honesty though, I can draft anything but normal cars. The trucks are easiest because they start slowly. However, SUVs are nice because you can see through them and look at what's ahead.

I won't draft on one particular street because there are manhole covers in the actual car lane, and they're not in the same spot every time. Some are in the middle of the lane, some are on the left side of the lane, and some off to the right, so I just don't ride in the car lane on that road. (I learned that lesson the hard way, was drafting and not thinking about it and hit a manhole cover very hard... didn't break anything and luckily I had just pumped up my tires that day so it was all good, was just... jarring.) However, on one of the main drags of town, it's slightly downhill with a few stoplights and no manholes (or potholes.) I love drafting on that road, easily rolling at the speed limit of 35 without pedaling on my heavy as hell commuter with full fenders and panniers. Great stuff.