Until now my top 10 would be:
1. Profondo Rosso
Truly the best Giallo. Argento is in total control of his art: every sequence is an artwork. It reaches perfection and stands miles above the other gialli.
2. All The Colors of The Dark
Unpredictable, groovy and sexy. Edwige, Martino and Nicolai at their best. The blend of giallo and gothic works perfectly.
3. The House With Laughing Windows
I love the atmosphere in this movie. The whole film seems to be haunted.
4. Tenebre
Cold, violent, elegant. This is the ultimate giallo. Every ingredient is there: the twisted mind, the naked flesh, the flowing blood, the sharp blade, the bleak urban landscape, etc... It's as giallo as it can be! It's, for me, the conclusion of the genre in its "classic" form. After that, most gialli are dispensable formulaic slashers.
5. The Strange Vice of Mrs Wardh
An excellent "sexy thriller". It's a surprisingly mature work for such a young director. The flash back sequences in slow motion are little masterpieces. I like how Martino manipulates us (you enjoy it, we'll she does as well!). It's a shame that the sadomasochist theme is put in the background in the end...
6. What Have You Done to Solange?
I rarely like "serious" gialli, but this one is an exception. Strong story, cast and music. And that Aristide Massaccesi knows how to use a camera!
7. Torso
A very good slasher with many iconic moments: the girl in the forest, the massacre at the end,... and if Tina Aumont is in it, it can't be bad!
8. The Night Evelyn Came Out of The Grave
It doesn't make much sense but I enjoy it a lot. The ending is a twist fiesta!
9. The Perfume of The Lady in Black
Barilli seems to be lost. Mimsy Farmer keeps climbing up and down the stairs, has visions, scream and cry,... I never understood what it was all about, and I like it that way! Visually it's a jewel. The romantic soundtrack by Piovani is also very good.
10. A Lizard in A Woman's Skin
I'm not a Fulci fan. Most of his film are depressing visions - saturated with misanthropy and nihilism. I know where he goes, and I don't want to go that way. A Lizard in a Woman's Skin belongs to his best period, when he was still an ambitious artist, not yet obsessed with putrefaction. The dream sequence in the beginning is fascinating. In this period, I like also Una Sull'Altra.
Mario Bava is missing, I know. I like his gothic tales (Black Sunday, Lisa & The Devil, Operazione Paura,...) but I find his gialli dull and artificial. They lack the sensuality, the madness and the violence of the ones by Argento, Martino or Dallamano. Some are even really sloppy (Cf. 5 Dolls for an August Moon).