I am a 'YUGE meganekko fan. I don't know why, but I often find them to be the more interesting of anime trope characters, especially when they know how to work them glasses. I also have too many favorites to list, but I will keep it to my current top three. (Hmm, some have already been mentioned, but here goes...)
(3) This one is a bit different for me. Mari Illustrious Makinami from the
Evangelion reboot movies. As insanely blood-thirsty as this girl can be when piloting an eva, with her wearing those cat-eye glasses while doing so just inverts her cocky, vicious attitude, which to me is usually off-putting, and makes her seem, yeah, sexy. It's just glasses, mind you, but, hey, it works. Cannot for the life of me explain.
(2) I don't think anyone has yet mentioned Mirai Kuriyama from
Kyoukai no Kanata (
Beyond the Boundary). She's easily one of the top ten, and she's so incredibly adorable. She fits the trope to a tee, as only Kyo Ani can.
(1) BUT my top pick for all-time best meganekko is, of course, the poster child for this forum question, Tsubasa Hanekawa from the
Monogatari series. "I don't know everything, Araragi. I only now what I know." Long hair, braids, or short hair, she's adorably hot and witty and cute. I did feel a bit betrayed when in later seasons she started wearing contacts, but I was already smitten, so I can overlook that. Also in her favor is that her aberrational form is that of ferocious cat-girl. A Mega Neko, or "Big Cat", if you get the pun.