My main areas of interest tend to be military non-fiction. To that end, and in no particular order, here are what I can remember right now:
Panzer Commander, kind of a memoir of Hans Von Luck and his years in the WWII german military
Feet Wet, assorted stories from a guy in Naval aviation going all the way back to the Langley
Rogue Warrior, this was Marcinko's first book, and I really liked it
Point Man, by James Watson, more real stories from VietNam Seals (possibly my favorite)
Marine Sniper, not mentioned above, and for new members, should be required reading to post (read this at least 4 times)
Snake Driver!, stories of helicopter war in VietNam
Six Silent Men, stories about LRRPs in VietNam