On Hoshana Rabba after one uses (Klaps) his Hoshanos may another person use the same Hoshanos?
Nitey Gavriel (Hilchos Sukkos pg. 378) quotes the Shu"t Zakan Aharon (OC 30) who proves from the Gemorah (see below) that Lechatchila one should not reuse another's Hoshanos. He (Nitey Gavriel) suggests that doing so is considered shameful to the custom of the Nevi'im of hitting the Arovos, and that since there are allusions to judgment and severity it is not considered appropriate to re-use them. However, he writes that in terms of the strict letter of the law there is no problem, and one would fulfill the minhag with a previously used arova.
[The proof of the Zakan Aharon is as follows: Firstly he proves that that it is permissible to use the arovah from the arbah minim for hoshana rabbah from the Gemora in Sukka 44. He then asks from the Gemora in Gittin 52 that the manager of the estates of orphans purchases a lulav and arovah for the orphans - as per above it would be sufficient to use the arbah minim for both purposes. He concludes that since the case in question is multiple orphans, although one lulav suffices, he needs multiple arovos for each orphan as we do not reuse them. However, he notes that it seems many did not have the word arovah in their version of the Gemora in Gittin 52 thereby negating the proof.]
Kovetz Halachos from Rabbi Shmuel Kamenetzky says that it is Mutar L'Chatchila to reuse so long as there are leaves remaining on the Arava.