The Walman language of Papua New Guinea has two interesting grammatical features: a conjugated and, and an inflectional diminutive.
Walman's verbs have polypersonal agreement on transitive verbs, marking both subject and object. Conjunction is handled with two verb stems, -aro- and <-a-> (subject is a prefix, object is a suffix):
mother 3SG.F.SUBJ-and-3SG.M.OBJ father
a mother and father
Since verb serialization is already present in Walman, it looks like a verb got grabbed to mean and and got dropped into the serialization chain. There is also a non-conjugated and, which may be used instead of the conjugated form, but seems to be preferred for inanimate constituents and clauses. Interestingly, the Lamaholot language of Indonesia also has an inflecting and, but it can be used to join clauses.
See Verbs for 'And' in Walman for all the glorious details.
Walman also has a third person singular diminutive marker which occurs on verbs and adjectives.
The puppy is barking.
The female dog is barking.
The male dog is barking.
The dogs are barking.
The authors of the paper below believe that the diminutive marker was originally a neuter gender.
See Diminutive as an Inflectional Category in Walman for details.