Henry

Henry is an Aperture Science Employee. He was working to prevent GLaDOS's murder attempts and developed the Morality Core as the solution. Henry was optimistic about the outcome of GLaDOS, while his co-worker Doug Rattmann was more suspicious. Later, when GLaDOS was activated for "Bring your Daughter to work day." Henry gleefully provided her with Neurotoxin for a recreation of the Schrödinger's Cat experiment. Henry is thought to be killed by her on the same day due to Neurotoxin poisoning. 

For Henry’s voice, I’d think a medium voice for him. He’s a very optimistic person. Very into what he’s doing. Tends to ignore the possible complications that may be caused with the GLaDOS situation. Has a kind of "Ahh, don't be glum, chum." Kind of mentality.