Cesium Fluoride, CsF - mp/bp 703/1231 °C, (8,8) coordination.

With five shells of electrons shielding its nucleus, the Cs⁺ ion with its low charge density resembles a big puff-ball which can be distorted by the highly polarizing fluoride ion. The resulting ion-induced dipoles (blue arrows) account for much of the lattice energy here.

The reverse of this would be a tiny metal ion trying to hold onto four relatively huge iodide ions like Lithium iodide.