Well, my top choice would be the “fart suit” I mentioned back on your “I think I found out something quite awful” thread.
I got the idea from a birthday card that shows a guy inside an “astronaut suit” and reads: “George liked the smell of his own farts so much he had a special suit constructed.” In the inside it says: Hope your birthday’s a gas! 
I bought it about 3 years ago, in my last visit to the States, but I like it too much to actually send it to someone. Anyway, I figure they should be expensive (definitely more than 25 bucks!). In attention to that, I have other suggestions:
I was going to recommend, following Johnny LA’s line of advice, The Matrix DVD or The Indiana Jones Trilogy. Since you don’t have a player–and unfortunately, neither do I–why don’t you ask them for the DVD player itself? If they truly love you they should take pity on you and buy one for ya. If they don’t, just erase them from next year’s Christmas shopping list! 
Also, this book should be a great present: Sharing the Universe : Perspectives on Extraterrestrial Life, by Seth Shostak. I presume you know him; he is not only the most outspoken guy from the alien-signal-searching Seti team, but he could be considered as “The next Carl Sagan,” in the sense that he has become one of the most likeable and knowledgeable popularizers of science and search for extraterrestrial intelligent life. His passion, drive, and dedication towards encountering our place in the Cosmos mirrors the late Carl Sagan, as does his personality. He also has a great sense of humor, a factor which, coupled with the very interesting thematic content, should make for a great read.
Happy shopping and Merry Christmas!!!
Johnny L.A.:
True, very true. Love is the best gift. The warmth and joy provided by your loved ones is far better than material crap. Nonetheless, material crap is really cool too. 
Merry Christmas Johnny!!!
Merry X-mas, and a happy new…Millenium!!!
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