I actually prefer all of the other hands mentioned in the OP to K-9. In fact, under most circumstances I am more likely to fold it than to play it. But I do remember one night winning a tournament, largely on the back of K-9.
It was deep in the tournament and after being coolered and drawn out on a couple of times, I found myself down towards the bottom of the leaderboard. I was in the BB, facing a button raise and decided to defend my blind with K-9. I flopped two pair and ended up taking the pot down. So when I found myself again looking K-9 the next time my blind came around, I decided "what the heck". Even though the pot had been raised and called in front of me I decided to give K-9 another whirl. This time I ended up making a straight.
After that, I kept playing K-9 for the rest of the night, raising and even calling raises with it. Before I knew it, I was ITM and close to the top of the leaderboard, largely due to the success I had had playing K-9. If I remember correctly, I do believe I ended up winning that tournament. I did catch a few other strong hands in there, of course. But for the most part K-9 was the horse rode to victory that night.
It didn't become my new favorite hand or anything like that. But nowadays, from time to time, I look down at K-9 and remember a night when I went from the bottom of the leaderboard to the top on the back of that hand and decide to give it a whirl.