A mercury cell is a small button-type primary cell that delivers a very steady, almost constant voltage from a compact package, which makes it well suited to small, low-power portable electronics.

The key selection factors are size and current draw: mercury cells are physically tiny and supply only small currents over long periods, so they fit devices that sip power.

A pocket calculator is exactly this kind of low-drain, portable device, so it commonly used a mercury button cell to run for a long time from a small cell.

Kitchen ovens are high-power heating appliances that run on the AC mains and cannot be supplied by a tiny button cell.

Televisions likewise draw their operating power from the mains supply, not from mercury cells.

Ceiling fans are mains-driven motors requiring far more current than a button cell can provide, so they too are ruled out.

Hence, the answer is Calculators.