May your Birthday be:
Abounding
Abundant
Accommodating
Accordant
Active
Adventuresome
Adventurous
Affable
Affluent
Agreeable
All heart
All right
Alright
Amazing
Ambrosial
Ambrosian
Amenable
Amiable
Amicable
Ample
Amusing
A-one
Aplenty
Appealing
Aperitive
Appetizing
Appreciated
Artful
As it ought to be
As it should be
Associative
Astonishing
Astounding
At leisure
Attractive
Atypical
Auspicious
Avid
Awesome
and...
Most of all, Happy.