I must admit that one of my favorite quotes from M:tG is one of the less rational ones:
Of course you should fight fire with fire. You should fight everything with fire.
-- Sizzle
Step 1: Find your cousin.
Step 2: Get your cousin in the cannon. Step 3: Find another cousin.
The card art of Browse gives this gem, which I think I may have posted before:
"If A=B and B=C and C=D, then do not get a job proofreading." - Quid's Theorem
But the best flavor text ever is still Martyrs' Tomb.
Here's the new thread for posting quotes, with the usual rules: