"Wheels" because Artie is my favorite character and much is revealed about him, he sings a solo, he kisses Tina, everyone dances in wheelchairs, and Puck shows he actually has a heart.
Wow!! This is definitely not an easy question, because the whole season was great, but if i had to choose i would have to say "Sectionals", because it just made me so happy to see how far the kids have come and how hard they worked to get there that it was really no surprise that they won. It was such a victorious episode that you couldn't help but be happy and excited!! And the kiss between Will and Emma, oh my goodness that was so awesome and i was soo happy to finally see it. I can't wait to see how their relationship is going to progress. I also liked the episode "Ballads", it really showcased Will's singing ability a lot and i love to hear him sing so much!! His and Rachel's version of Endless Love is in my opinion better than the original, and his mashup with Young Girl/Don't Stand So Close To Me, was superb.
I just love this show so much and i hope that it has longevity. I'm a gleek and proud of it. lol