I've been thinking hard about this and, while I read rather voraciously, it's the books that I read when I was 13-15 that stick out the most.
From that time period, the ones that stick out the most are:
Scewtape Letters
Out of the Silent Planet (can't remember if that's also the name of the trilogy or just the first book)
1984
Animal Farm
Fahrenheit 451
Every 2 years or so, starting from when I was 8, I come back and read the Lord of the Rings trilogy. So I think that one sticks out rather well.
The earliest bedtime stories I remember are the Hobbit and then the Chronicles of Narnia series.
When I was 17 I read an amusing book on analyzing and understanding algorithms titled 'Compared to What?' It was our course book for one of my senior comp sci classes, but, unlike a lot of my course books, that one actually stuck with me.
I need to add Atlas Shrugged to my list of must-reads.