I always and instinctively think:
Alison.
Even though, when I was at school, there were two
Allison people and one
Alison in my class.
Allison is needlessly complicated, and the one-L version shows the name's origin as a diminutive for
Alice very clearly. If I recall, two of them were sometimes called
Allie and one of the Allisons never had a nn. Doesn't
Allison derive from 'son of
Alexander'? It certainly is a lnfn, but they aren't much of a fad where I live; not yet, anyway.
I love
Alison! It's unusable for family reasons - DH had a really odd aunt - so I'd have settled for
Alice if anything, but
Alison is just as good.