G
from Fancyclopedia 2 ca 1959 and Fancyclopedia 1 ca. 1944
Ordinarily a well-behaved letter, except when people talk about its "soft sound" (meaning J) or retain it in words where it's silent with us. But G has been most grievously cursed with the purple poison of Ghughu, so that any word beginning with it (or for that matter many words beginning in H or other letters) may find itself altered to start with gh-.