We've all experienced them. Hero apparently gets killed. Wait a week. Heroine is drugged with creepy guy ready to rape her. Wait a month. Guy confesses suddenly to girl. Series gets canceled. Which series, anime or manga, and which cliffhanger really sent you up the wall? Also, are you the type to avoid these type of series or get painfully hooked to them?
Personally, I prefer to avoid them until they are completed. Sadly, I tend to be impatient and pick them up, hoping I'd have the willpower to stop during a more tame chapter or after a major story arc is finished.
For anime, my most memorable cliffhanger in recent memory would be the ninth episode of Kurenai.
Spoiler (highlight to view)
Seeing the pack led by the incest lover and the pyscho leaving with Murasaki after kicking everyone's asses... that scene was just nasty.
For manga, Kodomo no Jikan.
Spoiler (highlight to view)
A lot of the chapters end in a nasty cliffhanger but when Rin's father suddenly wanted to adopt her, waiting for the next month's chapter was a whole new level of pain.