This is years in the future for me, but I like planning ahead. Kilimanjaro is mostly known as a hike, but there must be ways to find something more interesting to do there.
I've seen some guidebooks where they describe rock climbing routes on the Breach Wall, but it's hard to find info on them. I've guessed it must be because those routes are chossy and dangerous, even if the technical grade is pretty easy.
The Heim Glacier is supposedly also an option, but even if there is glacier to climb, it must be hard to find a guide who wants to go. Considering it's mandatory with a guide on Kilimanjaro.
When I go there I plan on setting off a few weeks so I can both attempt Kilimanjaro and the north face of Batian (Mt. Kenya). Seems to be much easier to find guides for Mount Kenya.