i don't think you want your initials to be the name, stock symbol, and domain name of a giant telephone / internet / cellular provider that everyone hates. you'd be mocked by an adult community!
ATT -- alexander thomas tipke is almost too repetitive in the hardness of its consonants. plus, 'alexander thomas' sounds like some kind of founding father type name. talk about pedigree. too far in that direction.
AJT means nothing, and alexander joseph tipke is both easy to say and aesthetic; the r leads better to the j than it would to a t and the 'f' leads to the 't' better than an 's' would (though only slightly).
but that's just my analysis.
alexander jonathan just deserves a beating, and james puts a hard 'z' sound right before the hard 't' sound in tipke. bad.