Guild Wars 2

specific rewards for completing all the achievements within a category

such as relevant skins
wvw – crown skin
fractals – fractal weapon ticket (also maybe add a complete scale 40/50/whatever)
kegbrawl – keg backpeice

… or even just stuff already in game
wvw – badges/blueprints
fractals – relics/pristine relics (although pristine relics are pretty much useless by the time you get the final tier of fractal frequenter)
kegbrawl – karma… gold… something?