Brave SU-37 92890/61926 (A) +10% Air Attack: 1,670 gold
Brave Marksman 85149/69667 (I) +10% Inf Attack: 1,670 gold
Brave Warship (S) 68119/102179 +10% Sea Attack: 1,670 gold
I'm not sure if they stack, but if they do.. this is the worst idea Gree has ever had IMO. When you can just buy boost, all the excitement from completing events is gone.
EDIT:
Screenshots for those in doubt