This is the language I'm developing for Lexember. I figured I'd post what I have about it as well, so I can gradually add on. It's spoken in the Republic of Ayarang, a small country which is talked about (outdatedly) here.
Phonology
/i e a o u ɨ ə/<i e a o u ɨ ə>
/p b t d t͡ɕ d͡ʑ k g kʷ gʷ ʔ f θ s h m n ŋ ŋʷ r j w/<p b t d c j k g ku gu ' f th s h m n ng ngu r y w>
/ɨ/ is a marginal phoneme, mostly surfacing in loanwords.
I haven't fully decided on the nature of the distinction between what I've marked as voiced and voiceless stops. It might end up being an aspiration distinction instead.
The romanization I use is fairly provisional. It's also not what the speakers, who live in the real world, use; they have something much uglier that involves umlauts as well as a yet-undeveloped native script.
The basic permitted syllable structure is (C)(r, y,w)V(V)(s, m, ng, r).
As for allophony, I only have:
-/d/ --> [l] intervocallically. This is reflected in the orthography.
-/k/ /g/ /ŋ/ --> /kʷ/ /gʷ/ /ŋʷ/ before back rounded vowels. This means that the distinction between the two only exists in front of /i e a/.
-This isn't quite allophony, but the nature of permitted nasal coda consonants varies a lot between speakers and dialects. Some preserve coda /n ŋʷ/, which is lost in the standard, while many more have merged /ŋ/ to /m/ in coda position (thus to these folks, the name of the country is Ayaram.)
-This isn't allophony either, but note that "voiceless" stops become voiced when preceded by a prefix.
Stress falls on the final syllable, unless the penult has a coda consonant and the final doesn't, in which case it switches to the penult.
Morphology
Nouns are marked for case and definiteness.
There are five cases: the nominative (unmarked), the accusative i(n)-, the ergative/dative m(a)-, the instrumental ku(a)-, and the comitative n(ə)-. I haven't totally figured out how all these are used yet, though it has a split ergative alignment along aspect lines.
The definite article is s-. If it occurs before a consonant which is not /r j w/ or before a consonant cluster, it becomes its allomorph sV-, where V is the vowel of the following syllable.
ababa --> sababa
father --> the father
S
hona --> sohona
woman --> the woman
After a case marker, this epenthetic vowel is deleted.
nəshona
COM-DEF-woman
"with the woman"
Verbs are marked for aspect, evidentiality, mood, and polarity. The unmarked form of the verb is the imperfective visual indicative.
Evidentiality is especially complex; the language distinguishes four evidentials: visual, nonvisual direct, inferential, and reportative. These four combinations are marked using a combination of the prefix pra- (which indicates that it is indirect) and the auxiliary ci (which indicates that it is either nonvisual direct or reportative.)
Keleo ababa yowon.
sleep father 1p.SG
"My father is sleeping." (I saw it for myself)
Ci keleos ababa yowon.
NVIS sleep-PTCP father 1p.SG
"My father is sleeping." (I heard him snoring)
Prageleo ababa yowon.
IND-sleep father 1p.SG
"My father is sleeping." (I figure.)
Praji keleos ababa yowon.
REP sleep-PTCP father 1p.SG
"My father is sleeping." (Someone told me.)
Ci also means "to hear" when used as a regular lexical verb.
The conditional is marked with aj(a)-. The negative is marked with th(e)-. The perfective is marked with -s, which becomes -si after a consonant.