I want to gather up all words with variable gemination. (I know, really exciting.) Anything where there's some variability - including cases from Mediæval Latin or Neo-Latin. Here's what I've got so far:
bracchium, brachium
Brittones, Britones
cattus, catus
Juppiter, Jupiter
littera, litera
quattuor, quatuor
scacc(h)i, scac(h)i
Scotti, Scoti
Does anybody know of any others?