1. Limescale on taps, spouts and around the plughole
The white crust around the base of a tap is calcium carbonate, and it is alkaline. General bathroom sprays are mostly detergent and do nothing to it, which is why people scrub the same tap every week for years.
You need an acid. White vinegar at full strength works on light deposits. Citric acid powder dissolved at about two tablespoons per cup of warm water is stronger, cheaper by volume and far less smelly, and it is what most commercial limescale removers are built from. Both are safe on chrome.
For the base of a tap where the crust is thickest, soak a cotton pad or a strip of kitchen paper in the solution, wrap it around the joint and leave it thirty to sixty minutes. Wrapping is the key — a liquid sprayed onto a vertical surface runs off in ten seconds and never gets the contact time it needs. Re-wet the paper if it dries. Then scrub with an old toothbrush and rinse thoroughly.
The important exceptions: keep acids away from brushed brass, gold-effect, nickel and matt black finishes, where they strip the coating and leave permanent patches. Keep them off natural stone and marble entirely. For those, use a dedicated pH-neutral cleaner and rely on drying rather than dissolving.
Finish by drying the taps with a cloth. Ninety percent of visible limescale is prevented by removing the water before it evaporates.