Yeah. If I had to give a classic, it'd probably be Beowulf. Then the question becomes, which translation? I'd probably give a few copies of Burton Raffel's translation because it's very affordable, very poetic while still being easy to read, and it's honestly my favorite. Heck, I have three or four copies just because they're an easy gift to give. I'd probably give one or two copies of Seamus Heaney's translation too, because it's also quite good and it has the old English and Heaney's translation side by side and I always love it when publishers do that.
I think Frankenstein and Innocents Abroad would be fun to give too.