2. Seeing function come back after TPA administration. Normally we don't do MRIs prior to TPA, just CTs. The MRI suite is always so busy that holding TPA until we have a solid MR image would push most of our patients out of the window (in terms of time, not literal defenestration). That means it's always kind of a crapshoot in terms of what we'll see, depending on whether the embolus was a clot or plaque or whatever.
3. Learning even tinier details of brain anatomy every single day. Just when I think I've got a good handle on things, some genius comes up with a theory that a patient's symptoms are due to a minor derangement of Whargarrbl's Foci of Bolognese's Range of the Straits of Inglewhazzit. It all starts to sound like Terry Pratchett, and I'm off to the textbooks again.
4. Learning really gross things about gross anatomy. Turns out there's a nasty situation that can happen inside an artery that causes a big snotlike glob of fat and plaque to detach partway and hang there in the blood streaming from the artery. Except that it's attached at one end to the wall of the artery, so it just goes "hrrbl hrrbl hrrbl" and blops around, occasionally causing TIAs. I can't remember the name of it, but if I see it again, I'll know it.
5. Knowing enough to explain what's going on when somebody in a different department starts freaking out about the YouTube video with that octopus? That's dead, and in soup, but then somebody pours vinegar over it? And I can explain how the acid in the vinegar stimulates the sodium channels and makes the octopus-food-corpse-guy want to crawl out of the bowl. That's really cool. I like that part.