Building wiring could be made out of gold instead of copper or aluminum, simply because gold has the lowest resistance of room-temperature wiring. A gold/copper alloy (or gold-plated copper) might be the best choice for plumbing (due to gold's corrosion resistance, platinum is another choice here). Gold plating would be an option for metal roofs, car parts (which don't experience significant wear), fences, hulls of ships, antennas, and general electronics.
Gold is over twice as dense as copper or steel. That much weight could be an issue in a lot of those applications, particularly roofing. There's a reason why we use very thin metal roofing material: weight. Adding even a very thin layer of gold to that could have a negative impact on weight constraints. Also, gold is highly malleable, which is bad for any parts that are load-bearing or sustain impact events.
A list is only as strong as its weakest link. -- Don Knuth