I saw the thread on which cards to upgrade, and it got me thinking in reverse... as one who was pleasantly suprised to win a relic, and not knowing what to do with it, I upgraded it of course. Doh.
1. Relic - pointless upgraded
2. Sundial - a moot point, but it is used unupgraded the vast majority of the time.
What next? Giant frogs/Jade staffs are often unupgraded for the adreneline rush. For nymphs I note it is advised to keep unupgraded for tournies. I understand there are benefits to keeping certain dragons unupgraded? Any others...