Radak: Most say that it is musk. Malbim (Derech ha'Muskal) - it hints to the choicest of powers of the Nefesh ha'Chiyunis (just like musk is the best fragrance of animal origin).

Radak citing Rav Hai Gaon: It is a fragrant sap called Luvni in Arabic.

Radak: It is the fragrance called Sunbal in Arabic.

Rashi: Ketzi'asa is the Targum of Kidah (Shemos 30:24, one of the spices used to make Shemen ha'Mishchah - cassia). Radak - it is as if it says u'Ketzi'os; the prefix Vov is omitted, like "Shemesh Yare'ach" (Chabakuk 3:11).

Malbim (Derech ha'Muskal): Ohalos and Ketzi'os hint to the choicest of powers of the Nefesh ha'Tzomachas (just like Ohalos and Ketzi'os are the best fragrances of vegetative origin).

Rashi: All your garments smell like fragrant spices.

Rashi (from Yerushalmi Pe'ah 1:1): All Begidosecha (your betrayals) and sins get atonement, and have a pleasant smell.

Radak: The entire verse is a metaphor for good deeds - "b'Chol Es Yihyu Vegadecha Levanim v'Shemen Al Roshcha Al Yechsar" (Koheles 9:8).

Malbim: Even those who were Boged (betrayed) you and did not desire your kingship, they will throw on you nice fragrances when you go from ivory palaces. Then he went to greet his Kalah.

Malbim (Derech ha'Muskal): They are powers that betray and oppose the intellectual Nefesh. E.g., stubbornness and foolishness oppose becoming wise; envy, lust and similar Midos combat [intellect] in deeds. Their source is in the lower (animal and vegetative) aspects of the Nefesh.

Rashi: The palaces prepared for you in Gan Eden, to gladden you, are better than superior ivory palaces.

Radak: Your garments are brought to you from ivory palaces, where they are kept. The suffix Yud in Mini is extra, like "Mini Efrayim" (Shoftim 5:14). The ivory palaces gladden you; a beautiful dwelling widens one's heart.

Malbim: When you will go from ivory palaces, a place of Simchah, to nuptial Simchah, even those who betrayed you will throw on you nice fragrances for your honor.

Malbim (Derech ha'Muskal): Also the Midos from the lower aspects of the Nefesh will be submissive to the intellect. They will be converted to faithful servants of the intellectual Nefesh, e.g. to be brazen against people who mock Avodas Hashem, cruelty against those who anger Hashem and His enemies.