So I had thissy here idea; what if you gained Karma by gifting other players? A lion with the generosity of giving gifts to his comrades is certainly a kind one.
This would apply to giving items to other players through the link on their den page. When one user gifts another user, they'd receive positive karma for their kindness.

Obviously, though, it could probably be easily taken advantage of by just gifting really cheap things to a lot of people or back and forth between accounts; to prevent that, limits can easily be applied as to how much karma can be gained in a day or other time limit. To decide how much positive karma is gained, I was thinking it could run based on value (based on price at the Monkey Shop): for example, for every 500 SB-worth gifted by a player, they receive +1 Karma. There could also be limits as to how much karma you could receive from gifting a single person to prevent people taking advantage of alternate accounts. I think it'd be a really great idea to implement generosity as a beneficial thing, and give lions a positive reputation for what they do outside of Explore.

Edit: Other Ideas: (see comments, not all ideas mine)
- +Karma of gifts depending on Rarity of items, not Value
- Wishlists
- Ability to Enable/Disable Karma from gifting