Mine has this for its moveset, it covers all weakneses:
Earthquake: If a Ground type doesn't have this move, something is very very very very wrong. If a normal Pokemon with higher attack than Sp. Attack doesn't know Earthquake, the reason better be that you are low on TM 26. Even if a Pokemon with higher Sp. Attack doesn't have Earthquake, that may be wrong.
Ice Fang: Decent power, chance to cause flinching or freezing, decent accuracy, used to deal with Grass types. Also deals with Flying types, who are immune to Earthquake, and the ever popular Dragon type.
Thunder Fang: Decent power, decent accuracy, chance to cause flinching or to paralyze, used to deal with Water types. It also deals with Flying types, which are immune to Earthquake.
Stone Edge: High power, good chance for critical hit, used to deal with Ice types. Also deals with Flying types who are immune to Earthquake.