#1. His hair
His carefully trimmed curls were quite different from the hairstyle Presidents were meant to keep. He was known to whip out his comb on occasion to keep the errant curls in order.
#2. He was the man behind the Spacemen
He was one of the few scientists who worked at ISRO during the early years of the organisation, when a church was made the office and a nearby beach the site for a launchpad. He was also the Director of the project that indigenously developed the SLV - III which launched satellite Rohini and made India and exclusive member of the space club; and the PSLV, which was used in the Moon and the Mars missions.
#3. He was extremely humble
Once at a convocation at IIT Varanasi, Kalam noticed that his chair was larger than those of the other dignitaries. Once he offered it to the Vice Chancellor for that very reason, it was promptly (and one can only presume, awkwardly) replaced by a smaller one, just like the others.
#4. He loved children
Not in a forced avuncular way. He saw in them the future of India, and perhaps the boy he had once been, selling newspapers to earn for his studies. He celebrated his 80th birthday dressed in a full-sleeved grey safari suit around 25 km from Coimbatore, in a village where he was joined by hundreds of children and farmers.
#5. He was a futurist
From his love for powerpoint presentations to his adoption of Twitter, he was always enthusiastic about new technology.
#6. He was a great communicator
He was always happy to part with his email, apj@abdulkalam.com, or to share his website address. And once, as president, he posted the question "What should we do to free our planet from terrorism?" on Yahoo Answers.