emotional 

As calm as Alex may be, he is susceptible to small bursts of emotion that may sometimes come across as rather extreme.

A good example of this would be when he praises his physique.  The Major is often known to end up shirtless and sparkling in pride; though this is not the only time that such events are known to occur.

Let it be known, however, that despite the prideful outbursts, Alex is rather good at swinging to extreme lows as well; he is moved to tears by the Fullmetal Alchemist’s story.

manners 

Coming from a rather well off family, and being raised in the company of his siblings and somewhat snooty mother, Alex is well versed in manners.  Indeed, he a polite gentleman and when not angered or overly sensitive, he will act as such.

This gentlemanly attitude extends to both men and women alike, though the latter is more subject to his polite ways due to the current time period.

piano 

Despite his towering form and large, chunky fingers, Alex is a well practiced pianist.  Growing up, he was taught alchemy from his father and piano by his mother, discovering a passionate talent for both (though his alchemy takes the centre stage).

It was he who helped teached Catherine in her teenage years, after she’d began to learn the basics as a young girl.  This only intensifies his protective nature over his younger sister.

children 

Major Armstrong is well known for his soft spot, but it grows admirably when it comes to children.

He is especially fond of their usually shy and sweet nature;  the big friendly giant finds himself down on one or both knees, showering them with affection and sparkles. 

This stems from growing up as a protective older brother to his sibling Catherine, and from witnissing so much bloodshed of innocent children in Ishval.