I definately share a fondness for the duel between Exar Kun and Vodo-Siosk Baas myself. As for others, though, I can't really say; so many of the duels either occur in books without any visual aids or in Clone Wars-era comics that I couldn't care less about.
I do know I liked this duel that occurred in the Star Wars: Rebellion comic series:
A non-Force sensitive protagonist with a red lightsaber holding his own against two Force users? There's no way on Earth or any other planet I couldn't love that.
I must also mention the various duels in the Dark Forces Trilogy. At the time I first read those books, I didn't like the idea of darksiders wielding non-red lightsabers, but suffice it to say, I've more than warmed up to the idea since the prequels came out.
