Lip-synching skits are pretty much a no-no. They get boring and very awkward. I would recommend writing a skit with your own dialogue. It's more work, but the audience and judges will appreciate it a lot more.
Tsumugi Kotobuki - Waitress Ver. [ K-ON! ] - 100%
Yuki Nagato - Disappearance Ver. [ The Disappearance of Haruhi Suzumiya ] - 100%
Lara Croft - Reboot Ver. [ Tomb Raider ] - 90%
Kyouko Sakura - Casual Ver. [ Puella Magi Madoka Magica ] - 100%
Makoto Sawatari [ Kanon ] - 100%
Charlotte - Human Ver. [ Puella Magi Madoka Magica ] - 40%
Ayu Tsukimiya [ Kanon ] - 10%