1) My neck will ache on occasion; it makes a cracking sound when I roll it back, solving the pain.
2) My heart will occasionally skip beats, especially if coffee is involved. One day so much blood backed up that when it finally pulsed, my body jolted out of bed.
3) My eyes will twitch if I've been marathon-working on my computer (programming, web design, games, a damned viscious cycle).
4) My knees will sometimes freeze up or hurt so badly that my body will not physically use them.
5) On dark nights where the moon is blood red, demons will take over my mind and instruct me in the ways of darkness. My blood boils; that hurts, too.