Godfuckdamnit I love year end mash-ups!! They always give me goosebumps, tho I usually only see ones based on movies...
ANYWAY
1. Brown Eyed Girls - Sixth Sense
2. Wonder Girls - Be My Baby
3. Secret - Love is Move
4. Brown Eyed Girls - Cleansing Cream
5. Brown Eyed Girls - Vendetta
6. T-ara - Rolypoly
7. miss A - Goodbye Baby
8. Secret - Shy Boy
9. Rainbow - To Me
10. T-ara - Cry Cry
Reasons:
1 - Sixth Sense finally pushed me towards BEG fandom. From the very first few seconds into the song, you know it's going to be some FIERCE SHIT. But the entire song isn't just based on that; the chorus actually sounds like a celebration of life and pop music, one can shake her ass and bosom to it. It's just a powerful pop song, makes me feel invincible, etc. I'm only not a fan of the whistle note parts, but even then I appreciate that the members are able to sing those parts to begin with. Miryo's rap is flawless, as always.
2 - Be My Baby - I didn't like the video to this because they dance with such serious expressions on their face, and to me this song sounds so positive. So I ignore the video and just listen to the song. It makes me feel happy and joyful :3 And I love how little autotune stuff there is! You can actually hear their voices!!
3 - Love is Move - Such a catchy, fun song!! Haha I don't like the video to this either, because it's too focused on sexiness (what a weirdo I am), but the song is excellent to dance randomly to >o<
4 - Cleansing Cream - WHAT THE FUCK is shirenu voting for a BALLAD?? I'm just addicted to this song. And well, I love Ga In's husky voice. When I listen to this song, I feel like a blanket is wrapped around my shoulders. It's so pretty, dreamy, wonderful, my heart goes dokidoki
5 - Vendetta - Ok I am a BEG whore, deal with it. This is a track from Sixth Sense mini album, and it's groovy and catchy :3 It's a track I liked at first listen, which is quite a feat tbh.
6 - Rolypoly - I know this song is supposed to have a 60s theme or so, but I actually think of old school video games when I listen to it.

So it's a lot of fun. Just imagine a bunch of geeks dancing to this.
7 - Goodbye Baby - I suppose my favourite out of the srs bsnss tracks this year. It's catchy, but I still tend to find that a lot of miss A tracks don't have enough variation in them (it's often just the same beat throughout); I hope that's something that will change in 2012 and I'll be able to rank a song of theirs higher :3
8 - Shy Boy - I've got a bit tired of the obnoxiously cute card in 2011, but Shy Boy manages to just not cross the line to being annoying. It's a catchy, happy song

9 - To Me - Haha the English bits in this song actually bring it down to me a bit, I know, every Kpop song has silly English, but anyway. I think I've seen too many lives of this song, because I find the choreography boring, even Woori's "ballet bit" is too simple... So I love Rainbow, but I really want them to take it to the next level in 2012. Like "A" part 2 or sth.
10 - Cry Cry - Nice serious business song, but I think the video actually doesn't do it many favours. I mean, the video is way too long, making the song sound longer and epicer than it actually is. Then you get the track and it's only 3:18 long and doesn't actually have that much in it. It's still a nice song, it's just... short and doesn't live up to the expectations.
THESE WERE MY OPINIONS ^^ If some of these songs actually weren't released in 2011, let me know, but I think I saw most of them in the mash-up videos.