This brings up another issue that I'm not comfortable with in our game. As a type of handicap as was suggested, I don't give this player the type of magical gear that gets him excited. It's actually pretty hard for me to figure out what kind of magic items to throw his way. So compared to everyone else, he really doesn't have the cool stuff like other players. I feel bad about that.
He puts me in a bind here. I don't want to give him the items that I would normally give a warrior cleric, because that will just boost up his power even more. But when I give him fun/interesting magic items, he doesn't care about them because they don't improve the areas he's working to powergame.
When he created the PC, he dumped all his starting gold into +2 full plate & +2 shield & other AC boosting items and selected a nonmagical weapon. He did this assuming it would be easier to find a good magical weapon than it would to find +2 full plate. So I take that as a player trying to get the DM to powergame his PC for him without realizing it.
Overall, it's so hard to give him any magical item because no matter what I give him that benefits a cleric, it means that's one less area that he needs to worry about powergaming. So his focus goes towards improving the other areas more. He hasn't openly complained about other player's getting cool items and he hasn't...I just don't want him to feel like I favor other players sooner or later.