кто-нибудь

Pronoun

 * 1) (indefinite pronoun) anybody, anyone, somebody or someone (implies one does not care who, or does not have any particular person in mind)

Usage notes
The particle -нибудь is used more often in spoken speech, while the particle -либо is used more often in writing. Apart from this, they are largely synonymous, with their use subject to the stylistic and idiosyncratic preferences of individual speakers.

Declension
* Letter "" in genitive and accusative "кого́" is pronounced as /v/, not /g/.