I think that Major Armstrong is one of the funniest characters in FMA/FMA Brotherhood. He has so many funny scenes' and quotes. One of my favorite scenes is when he is fighting Greed's chimeras Roa and he turns his hammer into a mini statue of himself posing. hahahah.
Major Armstrong: (to Scar) Don't pray just yet, you're facing the technique that's been passed down the Armstrong line for generations, that's hardly a blessing
Armstrong: Edward Elric! (takes off shirt and poses) How dare you speak to your elder with such blatant disrespect! Let ME remedy this fight with my genteel decorum!