I'm thinking of a possibility of a bunch of special maps for achievements, which would disable certain tools so you have to do it a certain way.. like I dunno, reach platform x in under 5 minutes.
I would rather want titles, like when you finish an achievement called for example "Buggy Man" (enter the jeep x times...) you can chose this as your title which would show below you.
When you finish all you get "God Walking Amongst Mere Mortals"