In Northern India and southern Nepal, there is a language called Sunuwar, alternatively Kõits-Lo, Mukhiya, Kiranti-Kõits, Koinch, Koincha, and Koints. In 1942, Karna Jenticha developed a script for this language.
There have been two versions of Jenticha: the first was a pure alphabet: consonants did not have an implied vowel. However, in the second (current) revision, an implied vowel was added. I find it very interesting that someone could be surrounded by abugidas, deliberately design an alphabet and not an abugida, and then change his mind to stick in an implied vowel. I don’t know if he changed his mind, if his public clamoured for an implied vowel so they wouldn’t have to write as many characters, if he intended for there to be an implied vowel but his design was misinterpreted, or if he didn’t realize that there should be a vowel there. (One of my colleagues is a Canadian who learned Punjabi and Gurmukhi at home, and she honestly did not know that there was an implied vowel attached to the consonants in Gurmukhi because its sound in spoken Punjabi is so faint and subtle.)
Jenticha does not have vowel diacritics: to change an implied vowel, you write the syllable, then the next vowel. For example, to write “te”, you would write “ta”+”e”. The original version of the script did not have a virama or conjuncts — you don’t need those if you don’t need to kill vowels, but the later version does. Its consonant conjuncts are quite regular. There is a “half-form” of syllabic characters which are used in consonant conjuncts; those characters can also be interpreted to mean which means “the vowel has been killed”, i.e. as a pure consonant.
Jenticha’s glyph shapes are not obviously derived from any other individual language; it doesn’t “look like Bengali” or “like Devanagari”, for example. However, there are a number of characters which look very similar to glyphs in other languages: its “O” looks almost exactly like the Latin “O”, for example; the Jenticha “tha” looks almost exactly like the Limbu “tha”. There are even more letters which bear a resemblance: the Jenticha “ma” looks quite a like like a stylized Latin “m”.
Links: Unicode proposal
UPDATE: Based on personal communication with an expert, I fixed the name of the creator and the location of the creation.