I've had several. As I've spent more and more time training, they've become more and more "boring"--just about being in class and practicing. The ones I had when I first began training, however ...
The first one I ever had (well, it probably wouldn't be considered an aikido dream) was pretty weird. My sensei was teaching me how to train dolphins while balancing on a surf board, the balancing part being most important.
The next one started out as one of those "I'm being chased by a bad bad man" dreams, and just when I'm cornered and about to die, my sensei pops up out of nowhere and does some pressure point thing on this guy who was just about to kill me, which shorts the guy out and makes him fall. All the while, Sensei is nonchalantly instructing me. I, having settled down into seiza and acting as though this were just as natural as being in class, watch as he, while lecturing about details, repeatedly tosses the guy to the ground every time he starts to get up. Weird.