[@Mr Allen J] I have a few thoughts, although I'm highly unlikely to play more than one character.  

1. You Are What You Eat - taken to the extreme.  This character can both dissect what is in anything they consume, but also change their body composition to match anything they have eaten recently (or maybe just what they have eaten most recently). So after a soda, they could make their skin bubble, which would be a neat party trick.  Alternatively, they could eat a rock and then become a human statue at will.  

2. Environmental Control.  This character can absorb and direct heat and affect the temperature, humidity and barometic pressure (limitedly) of the space they occupy, up to a certain radius.  Also, they are generally invulnerable to heat and cold effects.  Directing heat would include superheating an item and taking heat from something (such as a cookie or oven).  This could potentially also include some degree of water control, as related to the saturation of water in surrounding air.  

Thoughts on either of these?