I know of languages (Arabic in particular comes to mind) where the subject pronoun can be dropped because verb conjugation encodes at least as much information as a pronoun might. I also know that there are languages which conjugate for both subject and object. My question is not about dropping those pronouns: Modern Standard Arabic, for example, still has "انا" even though conjugations uniquely determine a first person subject in all cases. But are there any languages where, not only can you drop the pronoun, but the uniqueness of conjugation means that explicit pronouns are not present in the language as separate words?
WALS chapter 35, "Plurality in Independent Personal Pronouns", by Michael Daniel, mentions several candidates:
two languages reported to have no plural independent subject pronouns or no independent subject pronouns at all: Acoma (Keresan; New Mexico) and Wari’ (Chapacura-Wanham; Brazil).
Languages lacking plural independent subject pronouns (type one) are extremely rare; each of the two cases in the sample occurs in one of the Americas (an additional such case, not in the sample, is the African language Mbay, which lacks independent personal pronouns altogether; see Keegan 1997: 62-63).
WALS chapter 43, "Third Person Pronouns and Demonstratives", by D.N.S. Bhat, contains the following section:
2.2. Absence of independent third person pronouns
Two of the languages of the sample are reported to have no independent third person pronouns as such. They are Cayuvava (isolate; Bolivia) and Wichita (Caddoan; Oklahoma, Kansas, Texas). In Cayuvava, words that translate as pronouns are derived by attaching the direct object personal affixes to certain auxiliary stems. These also function as auxiliary verbs (Key 1967: 34). In Wichita, on the other hand, personally inflected participles of the verb ‘be’ are given as translations of English pronouns (Rood 1976: 10).
As far as I know every known language spoken by humans has personal pronouns, even typological outliers like Piraha have at least some of them.
WALS chapters 39–45 deal with personal pronouns, the option "no personal pronouns" does not occur there.