If I were to rate usefulness of cards, I'd not hesitate a second to rate Sneak Attack 10/10. It is my "always needed/always wanted" kind of card. There are so many nice combos, some that I only discovered recently (w/Son of Arnor) and I look forward to the expansions to find ways to get Sneak Attack to my hand, either from the deck or (preferably) the discard pile. So far there is only Will of the West (which I don't play) that can bring it back.
What do others feel about it? Would you rate it 10/10 also?
and Sneak Attack in general. Sneaky Tooks have some use, too!