Jon,
I disagree in that there are more than a few things.
Deciding if a ball rests in causal water is highly open to whose ball is lying in the water.
Deciding if a something "man made" is in your way ala Ian Poultor just recently is speculative...he got two different rulings.
Deciding if a ball lies on hard pan or GUR because the mowers frequently travel over that patch can be hard to call.
As you said, deciding where a ball crosses the line of the hazard is another one I've seen where guys give themselves far more credit than where they actually hit it.
Coming to an agreement if "winter rules" will be in affect has caused some friction in money matches I've seen.
Deciding if a ball is on the green (and can be marked) or in the fringe has caused a ton on controversy in some of my own matches.
Deciding if a ball is OB or not depending on how one "lines up" the OB stakes...yes I've seen some ugliness on these ones, especially since its a potential "take the walk of shame" on the line.
And of course this also includes deciding what is and isn't a ball mark.
And those are just the ones I can think of. I'm sure guys like JVB have a whole booklet on "judgement" calls that exist out there where judgement must be used and its not clear vut
So once again, do away with all these rules and play it where it lies...ie don't touch it until its holed. Or do something about the completely awful divot rule to bring some real equity to the game. Not that I have a strong opinion on this or anything!!