Oohhh. Hard question. I would be torn between a couple of decks. My Thoth, because it was my first deck, and now that I've trimmed it, it really feels like "mine." But then, I don't read with it that often any more, so maybe one of my new loves, the Sakki-Sakki or the Robin Wood.
No, I'd probably go for my Thoth. It's been with me since I started my tarot journey 3 and a half years ago (I know, not that long
). Without it's borders, the deck really does feel like it's grown with me.
Incidentally, I once discussed burning this very same deck (in this thread:
http://www.tarotforum.net/showthread.php?t=31632) and now it's the one I'd save out of my entire collection
from burning. How very glad I am I didn't decide to burn it a couple of months ago!