The following is a list of nouns that operates in a different grammatical gender where it appears in the plural, or features two possible genders in the plural that offer two distinct meanings.
- balneum, -ī (n) bath —> balneae (f) baths
- carbasus, -ūs (f) sail —> carbasa (n) sails
- dēlicium, -ī (n) pleasure —> dēliciae (f) pet
- epulum, -ī (n) feast —> epulae (f) feast
- frēnum, -ī (n) bit —> frēnī (m) or frēna (n) bridle (the first the more common)
- iocus, -ī (m) jest —> ioca (n) or iocī (m) jests (” “)
- locus, -ī (m) place —> loca (n) places, but locī (m) topics
- rāstrum, -ī (n) rake —> rāstrī (m) or rāstra (n) rakes (” “)
Allen and Greenough also have this entry—
- caelum, -ī (n) heaven —> caelōs (m acc.) appears in Lucretius
This is an interesting case. According to Lewis and Short, it looks like the plural of caelum is actually lacking in Classical Latin except for a passage from Lucretius. However, caelī (m) meaning ‘heavings’ is frequent in Ecclesiastical Latin. Therefore, the evidence is inconclusive as to whether the noun is truly transgender.
The Essential A & G: 106b
Latin for Addicts 
I think I can shed some light on the plural of caelum in ecclesiastical Latin. The Hebrew idiom for the sky is plural, usually translated “the heavens”; So, Genesis 1:1, God created the heavens (השמים, ha shamyim) … Interestingly, when the Hebrew Scriptures were translated into Greek around the 3rd century BCE and some later, the translators stuck with the Greek singular, ὁ ουρανός. Except for whoever translated the psalter, which regularly features the plural, οἱ ουρανοί.
But by the time the New Testament arrives, the writers have adopted the Greek idiom. So Mark, probably the earliest written Gospel, records the baptism of Jesus thus: καὶ εὐθὺς ἀναβαίνων ἐκ τοῦ ὕδατος εἶδεν σχιζομένος τοὺς οὐρανοὺς (and immediately coming out of the water he saw the heavens being opened/rent, Mark 1:10).
Even an atticizing author such as Luke or the author of Hebrews follows this convention: Ἔχοντες οὖν ἀρχιερέα μέγαν διεληλυθότα τοὺς οὐρανούς…” (having, then, a great high priest who has passed through the heavens… Heb. 4:14)
From the Greek New Testament, the plural expression passes into the various vulgates and into Christian vocabulary.The Vulgate uses both the plural (igitur perfecti sunt caeli et terra, Gen. 2:1) and the singular, but the singular seems to be the neuter caelum (sit caelum quod supra te est aeneum, Deut. 28:23). A quick search did not reveal any masculine singular caelus. So, it looks like a genuine transgender plural, at least in late antiquity.
However, it appears the masculine form “caelus” was used in antiquity to personify the sky as a god. L&S note this usage, but the only really good example I could find was from the 4th century CE: “Caelus pater fuit Saturni…. ideo autem diximus ‘Caelus pater’, ut deus significaretur.” (Maurus Servius Honoratus, Commentary on the Aeneid of Vergil, bk. 5, l. 801)
Awesome!
“The follow is a list…” ??