Hi,
I am looking for Kdramas that don't have any love triangles (or only the tiniest bit)! 
Kdramas I have watched: Ugly Alert (My fav!), Secret garden (there was a tiny love triangle but it wasn't focused on too much, so it was okay), Lie to me (love triangle with the other brother wasn't the focus, so okay again), Coffee Prince (I really liked this drama!), The master's sun (There was a slight love triangle here, but it wasn't focused on too much), Rooftop Prince (slight love triangle, so okay), Kill Me heal me, Angry mom, Let's eat, the witch's romance. 
Thank you!
Have you watched Healer? One of the best K-drama that I have watched and has no love triangle from what I remember!
I second Healer, there is kind of a triangle but it's more like a two person thing there isn't really a third person involved. Also:

It's Okay That's love
King2Hearts
Pinocchio (from what I remember there is a bit of a triangle, but it doesn't really play a big role)
Cheongdamdong Alice (and this one from what I remember is like Healer it's more of a two person triangle)
You're All Surrounded

I also want to say possibly Emergency Couple, I believe there is a bit of a triangle but I don't remember it playing a big part.
Pasta's love "square" was similar to Coffee Prince, in that the second leads weren't serious competition & all of them actually had an interesting dynamic & history together.. tho there is a bit of unrequited love on their part for the main leads, I thought it was handled rather well ^-^ & I don't remember much of the series revolving around it (at least not as much as many other series).. tho some of my fave bits were ~because of it ;P 
Reply94.. well the series ~intended to center on a triangle, but it doesn't really count, in my opinion, because the other character is so extremely neglected not just by the writing, but by the other chars too, lol.. which may be painful to watch (ugh, the angst, my heart.. can barely take it) BUT the series itself was just so.. loove, it truly is more of an ensemble story, because how could anyone not love that whole cast? (& like Pasta, no "mean girl" cliche to suffer thru! tho the love square does have an unusual fourth corner, but it's so subtle, it practically was never even there.. heh >.>) I can rec fanvids if you don't mind slight spoilers.. like this hilarious masterpiece: http://youtu.be/-PCHxWtPcEk 
ShutUp: Flower Boy Band.. elements of typical triangles all over (& in various directions- even btwn a few of the band members themselves.. lol) but it's really all in the background, compared to the band's journey together xD
The Princess' Man
Bang Ja Chronicles - this has a +19 rating for adult content
HEALER!! You won't go wrong!