Well this is what I got for the intro to Fireflies, i know its not exactly like it but 
close enough. If it sounds too low to you, just move up the capo.
Standard tuning
Capo 3rd Fret

e|-------3-----0----------------0----------------------------------|
B|------------------------3-1-3------------------------------------|
G|----------------------0----------------------1----------------0--|
D|--------------------2---------------0--2-0-2------0-2-0---0-2----|
A|----2------2----2-3---------------3-------------3----------------|
E|--3------3-------------------------------------------------------|

e|-------3-----0---------------1-0-----------------------------------------|
B|-----------------------1-3-1-----3-1----------------------------------1--|
G|---------------------0---------------------2-----0-----2-----0------2----|
D|-------------------2---------------------3-----3-----0-----0------3------|
A|----2------2---2-3---------------------3-----3-----3-----3------3--------|
E|--3------3---------------------------------------------------------------|


There ya go :)  comment on any corrections you have