Hmm I guess lamest 40k argument I've had was with Drax awhile back, reguarding weither or not Seraphim could deep strike. It was just a friendly debate and there were no ill feelings ( well I dont think so anyway), and it all pretty much ended with my foot deep in my mouth. Drax still likes to tease me about it every now and then
The debate ended when I took out my Codex and slammed it down on my bed and proudly started to quote it line for line... All was fine untill I realized the codex said absolutly NOTHING about Seraphim being able to deep strike... Needless to say I felt like an absolute TARD