A lot of these words I can find only in the newest edition of the Scrabble dictionary:
One syllable:
ball, bell, bill, boll, bull [boll=seed capsule]
dan, den, din, don, dun [dan=martial artist]
fan, fen, fin, fon, fun [fon=variant spelling of foehn]
far, fer, fir, for, fur [fer=for]
hack, hick, heck, hock, huck [huck=cotton toweling]
hap, hep, hip, hop, hup [hep=hip (stylish); hup=marching cadence]
mad, med, mid, mod, mud [med=medical (as in “med student”)]
nab, neb, nib, nob, nub [neb=nib; nob=rich man]
pack, peck, pick, pock, puck
sax, sex, six, sox, sux [okay, so I could only find “sux” in the Urban Dictionary ]
Mixed number of syllables:
tale, tele, tile, tole, tule [tele=television; tole=lacquerware; tule=a fabric]
Two syllables:
dally, delly, dilly, dolly, dully [delly=variant spelling of deli]
hallo, hello, hillo, hollo, hullo [they all mean the same thing]