Just a question I've been wondering about the answer to.

Love.

Yes, there have been plenty of times when he has been shown to be feeling other emotions such as guilt and regret

He feels a bunch, but his main drive is rage.

Take this panel for example:

Even Big Red knows Hulk can feel more than anger.

Yes. Hulks a whole persona in his own right with his own goals, dreams, fears etc. At times he becomes almost an avatar of rage but much of the time he has other stuff going on. According to Peter David the Grey Hulk was more a product of the selfish, lustful emotions that Banner felt uncomfortable with as a teenager than anger (unlike the Savage Hulk who was associated with Banner's childhood) anyways.