Rhinoceros, rhinoceroses and rhinoceri are all accepted to mean more than one of these nose-horned mammals.
Schema comes from Greek; it’s original pl. n. is schemata. Nowadays either schemas or schemata are accepted as plurals of schema.
The plural of self is selves. Like most nouns that come from German and are sibilants, self takes on -ves as a pl. n. form.
Stigmata and stigmas are both accepted plural forms of the singular noun, stigma. Stigma comes from the Greek, and is originally stigma/stigmata.
The plural of the Latin noun, colloquium, (pronounced koll-o-kwee-um) is colloquia or colloquiums.
Focuses is now much more commonly used as the plural of focus. Foci is also correct.
Genuses and genera are both accepted plurals of genus.
The plural of larva is larvae or larvas.
Locus, which comes from the Latin word meaning, “a place” (as in, location), has loci as its plural noun form.
Platypus, also called the duck-billed platypus, accepts either platypi, platypuses, and platypus as a plural form.