http://memegenerator.net/Overly-Obsessed-Girlfriend
Here's the origins of this meme: http://knowyourmeme.com/memes/overly-attached-girlfriend
I use it as is because she looks creepily happy, which is what I imagine students think teachers look like when they make "cruel" decisions.
http://memegenerator.net/Bill-Lumbergh-Office-Space
I could use this for rules or silly points I'd like to make such as being late, being messy, etc.
I could use this one to clear up misunderstandings.
For all the derp things.
http://memegenerator.net/Charlie-And-The-Chocolate-Factory
Sarcasm attack!
http://memegenerator.net/Brace-Yourself
http://memegenerator.net/Victory-Baby
http://memegenerator.net/Annoying-Facebook-Girl
I'll probably use this one either to make a point about grammar (since poor grammar usage is part of the meme) or for something I'm super excited about.