I don't count the combination of techniques that he knows (Sexy Jutsu and Harem Jutsu) as their own techniques since they are just variations of the original (transforming into a naked woman and using clones to transform into a group of naked women). Other than the three that I originally listed and variations of those three, I don't think that Konohamaru has used any other abilities in the manga.
As for the Third Hokage, there is a reason that Orochimaru is laughing. I know that he was known as The Professor. However, if he knew every technique in Konoha and could do them effectively, why didn't he during his battle with Orochimaru? Any of the Nara clan's shadow techniques would have been effective against Orochimaru; Naruto used the Rasengan numerous times in the war to take out Edos - the Third could have used them on the First and Second Hokages; we know that Orochimaru is susceptible to genjutsu; releasing the Eight Gates would have probably been enough to beat Orochimaru (Tsunade almost beat him with taijutsu); any form of taijutsu for that matter; Shizune's Poison Fog would have been good to create some distance; etc. My point is that even though they are known for their skills and knowledge of techniques, both Hiruzen and Asuma showed very little of their supposed potential that is constantly mentioned throughout the series.
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And as for konahamara he has used 2 of the 3rd hokages justus or is it 1 of the 3rd & 1 of asuma :| the smoke justu & shiruken clone justu