Instead of oil it could be methane as we all know of a world where it does rain methan whigc then flows in riveres and pools in polar seas... Introducing Titan the second largest moon in our solarsystem and only one with a substantial atmosphere 1.4 times denser than earth and vastly colder
I think I might have posted that somewhere in there, but if not I can add that in as well. Edit: I have sulfur, and I kinda thought that covers it, but I'll add it once I get time.
Water, lava, acid and flammable tar are all we need really. I wouldn't mind a less goopy tar like oil, but other than that some of those liquids sound... Unfitting.
More methods of Destruction is always better. While i'm here... I can't remember anymore if Liquid Mercury has been submitted as an idea yet...
I'm pretty sure it is, although quicksilver is a creatable compound, mercury as far as I know is not.
Your original idea has merit, but the sheer number of different types concerns me. I would simplify the idea somewhat: Acids - A generic 'harmful' liquid that comes in a variety of colors. Different colors could perhaps indicate different strengths of acid. Hydrocarbons - Black, flammable liquid. Does no damage directly, but burns impressively when ignited. Sludge - A useless, harmless slime created when two different types of liquid mix.
I did, re-read the thread. I'll add hydrocarbons and sludge, but I'd like to keep acid the way it is. Otherwise it'd be too hard to identify.
... now I really, really want some kind of molten rain. It would be an absolutely hilarious environmental hazard. "Oh hey, that volcano is erupting in the background and OH GOD EVERYTHING IS ON FIRE."
Ashen 'snow' would also be interesting. Such already exist in reality, such as on Io; the entire planet's surface is covered in several hundred feet of sulphuric ash, belched up by constant volcano eruptions deep beneath the ash layer. I could imagine that landing on a highly volcanic world would be all sorts of fun - fiery molten 'rain', ash 'snow', dusty 'fog', superheated tornadoes and other intense wind phenomena, and 'rivers' full of molten rock.