Thank you all for your suggestions! Although none of them were successful (his aversions are just too strong), I truly appreciate the input.
Some other failures of mine were:
Coating the pill in Magic Shell. In hopes that when he put it in his mouth, the chocolate would start to melt and he would be ale to swallow it.
Cutting a slit in the back of a Gummy Bear and inserting the pill. Also in hopes it would just slide down.
Inserting the pill into a marshmallow. Same idea.
Luckily, he was able to keep down baby aspirin (most of the time). He could only handle one aspirin, which is not even a full dose, but at least it was something. Jaysen's fever broke that night, and he is back to his ol' self.
He's also been getting nosebleeds for a few months now- I sent him back to school yesterday, and when I went to get in my car to go to work, his bus was in my driveway! My immediate thought was, " ohmigod...did I put him on the wrong bus?"
I ran out to the bus to find the aide trying to smother a child with kleenex. Upon closer inspection, I realized that the child in question was mine, and the aide was not trying to smother him, but rather trying to stop a bloody nose. It was bleeding pretty heavily, so they turned around and brought him back home. Free day out of school.
As Murphy's Law would have it, Jaysen is better, and Rylan is now sick. Same thing with the high fever, no other symptoms. Rylan will take meds to some degree (he can, he just doesn't want to) so I'm not tweaking about that just yet.
The most ironic part of this whole sickness episode? Jaysen telling Rylan to stop crying and take his medicine so his fever will get better. He's also encouraging Rylan to eat his chicken soup.