Can Gai use ninjutsu or genjutsu? It has been mentioned that Rock Lee can't use them, but I don't remember Gai using them either. I haven't read the manga.
From Naruto-wiki:


  Unlike Lee, who specialises in taijutsu because he cannot use ninjutsu and genjutsu, Guy is fully capable of using the other two forms of ninja abilities, as he is proficient enough to dispel a high-level genjutsu.


actually he summons this turtle multiple times in the manga