Fantasy: Can't narrow it down to just 2, too many entertaining characters out there! First is Buiva, the old god of war from the Tales of the Bard series (and by extension Owen the weapon master, since I thought they were practically identical characters). Then Decado the Icekiller, from David Gemmell's 'The King beyond the Gate'. Then Tomas/Ashen-Shugar from the Riftwar. Then the Patrician of Ankh-Morporkh. After them comes most of the characters David Gemmell has written (guess I'm a fanboy), followed by a good half the characters from the Feist/Wurts Empire series.
Sci-Fi: Alot easier for me... Odetta from the Dark Tower series & Orion from the series of the same name.