* Salt (NaCl): Salt lowers the freezing point of water, meaning it takes a lower temperature for the water to freeze. This is why salt is used on roads and sidewalks in winter to melt ice and snow.

* Sugar (Sucrose): Sugar also has a slight freezing point depression effect, but it's much weaker than salt.

* Pepper (Black pepper): Black pepper has no significant effect on the freezing point of water.

* Artificial Sweeteners: Most artificial sweeteners have little to no effect on water's freezing point.

In summary: Salt is the most efficient substance for melting ice due to its strong freezing point depression effect.