Henry IV of Castile had acromegalia and probably some form of gigantism, along with a number of other health problems discussed in this paper (http://historia.aeu.es/ArchEspUrol/LVI(3)207-245.pdf) (in Spanish). He was 1'80 meters tall, not as impressive today as it was in 15th century Spain. His father, John II, was around the same height and had similar features.

Wikipedia actually does a pretty good job at summarizing everything. I know copy/paste stuff is usually frowned upon, but this is pretty simple and I didn't have to go through my copy of The Two Lives of Charlemagne to find the same quote.

Charlemagne's personal appearance is known from a good description by a personal associate, Einhard, author after his death of the biography Vita Karoli Magni. Einhard tells in his twenty-second chapter:[85]

"He was heavily built, sturdy, and of considerable stature, although not exceptionally so, since his height was seven times the length of his own foot. He had a round head, large and lively eyes, a slightly larger nose than usual, white but still attractive hair, a bright and cheerful expression, a short and fat neck, and he enjoyed good health, except for the fevers that affected him in the last few years of his life. Toward the end, he dragged one leg. Even then, he stubbornly did what he wanted and refused to listen to doctors, indeed he detested them, because they wanted to persuade him to stop eating roast meat, as was his wont, and to be content with boiled meat."

The physical portrait provided by Einhard is confirmed by contemporary depictions of the emperor, such as coins and his 8-inch (20 cm) bronze statue kept in the Louvre. In 1861, Charlemagne's tomb was opened by scientists who reconstructed his skeleton and estimated it to be measured 1.90 m (75 in).[86] An estimate of his height from a X-ray and CT Scan of his tibia performed in 2010 is 1.84 m (72 in). This puts him in the 99th percentile of tall people of his period, given that average male height of his time was 1.69 m (67 in). The width of the bone suggested he was gracile but not robust in body build.[87]

edit: whoops, forgot the link: http://en.wikipedia.org/wiki/Charlemagne#Appearance /edit

87: ^ Ruhli, F.J.; Blumich, B.; Henneberg, M. (2010). "Charlemagne was very tall, but not robust". Economics and Human Biology 8: 289–290.

Kinda funny considering his dad was "Pepin the Short" although I don't know whether the name was valid or not.

The Roman emperor Maximus Thrax was described as being a man of gigantic stature, and he was often depicted in art in such a way. Some historians believe he may have suffered from Acromegaly, one of the conditions often described as "gigantism." This is believed due to frequent depictions of him (coins, for example) as having a very prominent jaw, brow, nose, etc, which are common symptoms of this condition. Here's an example:

http://upload.wikimedia.org/wikipedia/commons/3/36/Maximinus_Thrax.jpg

However, lot of the non-visual descriptions of him come from the Augustan Histories, which is not usually considered to be the most trustworthy of sources. Then again, the coins were contemporary, so it's hard to say.

US President Abraham Lincoln is thought by some to have had the genetic disorder MEN 2B, which causes (among other things) unusual height.

See www.washingtonpost.com/wp-dyn/content/story/2007/11/26/ST2007112600664.html.