Lemon balm
From Cookipedia
Lemon balm (Melissa officinalis), is a perennial herb in the mint family Lamiaceae, native to southern Europe and the Mediterranean region.
I feel it's culinary uses are limited, as to me, it's flavour and scent are slightly medicinal. Coupled with the fact that it can be a rampant garden pest, I would use a lemon mint or a combination of lemon zest and fresh mint.