Astrophe
Asylum
Asymptote
Atair
Atari
Ateesha
Athalia
Athena (Goddess of War)
Athene
Athens
Athinai
Atilla
Atinna
Atlantic
Atlantis
Atlas
Atom
Atossa
Attacker
Atte
Atti (short for attitude)
Atticus
Attila
Attitude
Atude
Aubergine
Aubrey
Audacity
Audball
Auden (named after the poet W.H. Auden)