seconding King 2 Hearts, Oh My Venus, and Descendants of the Sun.
*Sassy Go Go- The love triangle is almost non-existent. The love triangle develops halfway through the drama and the guy never even does anything about his feelings for her.
*Playful Kiss- No love triangle at all. There's a Japanese adaption too. It's called Itazura Na Kiss
*Kill Me Heal Me- Unless you count other personalities
*City Hunter- This one doesn't have a love triangle,but I got bored with it really quickly and it dragged on too long