Replace <USERNAME> and <PASSWORD> with your nicovideo login details. This is used to avoid thumbPlayKey errors when downloading. You can try removing these flags, but you'll probably get errors.

KMB
youtube-dl www.nicovideo.jp/watch/29850887, www.nicovideo.jp/watch/29686163, www.nicovideo.jp/watch/sm29887759, www.nicovideo.jp/watch/sm29437316, www.nicovideo.jp/watch/sm29813000, www.nicovideo.jp/watch/sm29825034, www.nicovideo.jp/watch/sm29662210, www.nicovideo.jp/watch/sm29802458, www.nicovideo.jp/watch/sm29761248, www.nicovideo.jp/watch/sm29851153, www.nicovideo.jp/watch/sm29949582, www.nicovideo.jp/watch/sm29738698, www.nicovideo.jp/watch/sm29851355, www.nicovideo.jp/watch/sm29502382, www.nicovideo.jp/watch/sm29417051, www.nicovideo.jp/watch/sm29561723, www.nicovideo.jp/watch/sm29847419 -u <USERNAME> -p <PASSWORD> -o 'Pack 17/KMB/%(title)s-%(id)s-%(uploader)s.%(ext)s'

Idolmaster:
youtube-dl www.nicovideo.jp/watch/sm29930221, www.nicovideo.jp/watch/sm29622260, www.nicovideo.jp/watch/sm29444200, www.nicovideo.jp/watch/sm29240142, www.nicovideo.jp/watch/sm29890681, www.nicovideo.jp/watch/sm29541463, www.nicovideo.jp/watch/sm29401558, www.nicovideo.jp/watch/sm29840202, www.nicovideo.jp/watch/sm29647250, www.nicovideo.jp/watch/sm29386942, www.nicovideo.jp/watch/sm29227123, www.nicovideo.jp/watch/sm29541606, www.nicovideo.jp/watch/sm29621837, www.nicovideo.jp/watch/sm29655920, www.nicovideo.jp/watch/sm29414384 -u <USERNAME> -p <PASSWORD> -o 'Pack 17/Idolmaster/%(title)s-%(id)s-%(uploader)s.%(ext)s'