[My2Cents]

Good question (about Wormtongue's tear). I believe it was a tear of "joy," as your friend suggested. There was nothing in Grima which indicated anything of humanity; nothing redeemable (although, I believe that Tolkien personally believed that no one was beyond redemption). He was utterly corrupt (even more than Smeagol perhaps?). His tear came, I believe, as he was touched by the "thing of beauty" that was Saruman's army. It was, to our sensibilities, a disgusting show of depravity.

[Elenya]

His tear came, I believe, as he was touched by the "thing of beauty" that was Saruman's army.

That's how I interpreted it too. Feeling the sheer power of Saruman's magnificient army would bring tears to the power hungry Wormtongue's eyes.

[sweetliberty]

I disagree that the tear shed by Wormtongue was one of joy. Joy is something that erupts from the fullness of the soul and does not coexist with evil. It struck me that this was most definitely an insight into what he had sold himself to, never having imagined that that such utter destruction could be imminent and that realization stirred what was left of his human soul with a pang of regret.