Is an Esrog Muktzah on Shabbos?
Esrogim of personal use: Esrogim which one has bought for personal use are not Muktza on Shabbos, as they are fit to be smelled. This applies likewise on Shabbos Chol Hamoed, as although they may not be smelled during Sukkos, including Shabbos Chol Hamoed, nevertheless they are not Muktza.
 SSH”K 20/21in name of Rav SZ”A.
 However Tzaruch Iyun from Ashel Avraham Butshesh end of 308 which implies that food never becomes Muktza. Vetzaruch Iyun.
 Michaber 658/2
 Seder Birchas Hanehnin 11/8
 Michaber 658/1. This applies even in accordance to the ruling of Admur in Seder ibid that one may not smell the fruit even on Shabbos, as the reason for forbidding the smell is because there is a doubt as to whether one is required to say a blessing. However according to all there is no prohibition in smelling it. Hence on Shabbos one may make a blessing on the smell of another fruit and than smell the Esrog. Therefore the Esrog is not Muktzah. [Mishneh Berurah 658/5]
 As they are designated for smelling and may be smelled on Shabbos. [See Michaber 653/1 and Sharreiy Tziyon 658/2]
 M”B 658/3
 Michaber 658/2; M”B 658/3
 As they serve absolutely no use.