One of my old English teachers back at my old school left, not sure why but there'd been rumours for ages beforehand that she'd seduced a Sixth Former at her previous school. Also, we apparently had a convicted paedophile as a Design teacher while our regular teacher was on maternity leave. One guy teaching us mechanics (Particle Dynamics for my fellow university Maths students) in Maths decided the only way to teach vectors and motion of particles was to throw a pen around the classroom. He was crap, basically. His successor taught us things in the wrong order by giving us work to do on topics we knew nothing about, and we almost all failed that module at A-Level. Finally, my GCSE ICT teacher was responsible for marking my coursework and then sending it to the exam board for moderation, so he effectively had complete control over my GCSE grade. He hated me and always marked me down, yet I still managed to get an A because I was that good at the written exam. He seemed pretty surprised when he found out what grade I'd got, incidentally...
Yeah, I've had my fair share of crap teachers. Oh, and my Applied Maths tutor this year at university was absolutely appalingly bad. Ironically he's also my Personal Tutor so I couldn't complain to anyone because I'd basically be filing the complaint with the accused, which kind of defeats the point of filing a complaint with your Personal Tutor...
EDIT: Almost forgot, I actually threatened to hit my old Games teacher with a hockey stick back in Year 8... I can't remember it but my friends have never let me live it down xD