Ritsu Tainaka is really underrated. She deserves more appreciation

Ritsu is my personal favorite character, I never really thought about it much but now that you mention it I do think Ritsu is one of the lesser brought up characters. Naturally Yui I think is most talked about though

Massive forehead and all I love her so much, she's the absolute mood of the band, to be fair Ritsu showing her forehead is asserting dominance because no other anime character I've seen could attempt that exact hair-style and still look so cute! I quite like it myself, it gives off energetic, optimistic, headstrong, and girly vibes while sharing subtle spikey rockstar feels, without the head band I doubt Ritsu with her hair down would be as surprisingly cute anyways.
She's so cute and funny while being completely self-conscious that she is cute and funny, in comparison, Mugi is cute because we know she is innocent, and Yui does funny things but she's too dumb to realize it(which makes it funnier?), at last, what is always funny to me is that Ritsu's mannerisms are tomboyish but she drops it immediately when she can't keep up with it(especially when she angers Mio or Sawa-chan off).

I'm aware that the gag is Ritsu is scatterbrained and Mio is the diligent one, however Ritsu in my opinion represents the club and its atmosphere from the first episode, in a similar manner she's fit as the leader/president same way to Haruhi Suzumiya. Yui is the mascot, and Ritsu is the title Light Music Club!

Yup, Ritsu is best K-On girl, personality and looks.