My absolute favorite is the firefly tour! Not because of the medals, but because I love the quiet atmosphere of a night tour and the faint glow of the fireflies. And it was the only way for me to see fireflies up 'till now, 'cause I started the game in September.
I also like the gardening one, tho, because it's easy and you can get flowers for your village. And the Tuna Kahuna because HOLLY POTATOES MEDALS GALORE yeh
My favorites as well!