If I receive a monetary gift, do I need to give ma'aser on it? What about if I receive a gift that is an object (as opposed to money)?
Rabbi Breitowitz gave a lecture a few years ago on Ma'aser (I don't believe the audio is posted anywhere). He said it includes gifts, but only if cash, which you can use for anything. Not non-monetary gifts, and not gift certificates. (Note that many couples do a bridal registry someplace where they can return their gifts for cash; if you cashed it in, you'd then take ma'aser on it.)
Rabbi Yitzhak Hirschfeld told me that if cash is given in lieu of a specific gift, because it is easier to ship or such, then that money too does not need to have maaser taken. He mentioned his mother wanted to send him furniture, but it was easier to mail a check and a note instructing him to buy furniture with the money.
There is no maaser on non-monetary gifts according to R Tzvi Spitz, R Moshe Feinstein, R Moshe Heinemann, Chazon Ish (all four cited by R Avrohom Chaim Feuer in The tzedakah treasury pp. 136-7).
Some disagree, e.g., Rabbeinu Yonah, R Shlomon Zalman Auerbach both cited by R Shimon Taub in The laws of tzedakah and maaser
Others hold that only if one would have purchased the gift anyway is one liable to maaser, otherwise not (צדקה ומשפט).
On monetary gifts, Minchas Tzvi rules that there is no maaser obligation because the donor doesn't want his money to be used for anything other than his specified purpose.
On the other side, R Chaim Kanievski disagrees (in Derech Emuna, Tziyun Halacha 67) and cites his uncle the Chazon Ish who rules that one must give maaser from the full amount of the gift even if the money was earmarked by the donor to be used exclusively for a specific purpose. Rationale is that the donor would usually not object if the recipient used some of the gift money for charity. Only if the donation to charity would prevent the recipient from fulfilling the wishes of the donor would the recipient be allowed to purchase the object, BUT he would need to donate maaser later.
R Shimon Taub also writes one needs to donate maaser from monetary gifts (he writes it is pashut - obvious).
So with this diversity of opinions, in practical cases CYLOR.
I asked Rabbi David Feinstein about this once. He said the value of the gift would be the deciding factor. The following were his own examples. A small gift 20 dollars or so from your grandmother would require having Maaser taken as she wouldn't mind if you gave the couple of dollars away. However if she gave you a new car, she would not want to have given it in a way where you would incur a such a large bill, so we can assume she gave it with a stipulation of not needing Maaser to be taken.