When you open up a codex you get the fluff then the rules, and sometimes the fluff doesn't really fit the rules. What first springs to my mind are blood angel devastators. So I want to know which codex missed the mark the worst and which codex hit the nail on the head.
I would say for the best fluff to rules army would be the orks. Get a lot of boys and crazy ramshackle war machines together and run at the enemy fits pretty good i think.
The worst I think would be the tyranids. I don't really like how GW really pushed the big monsters, when I think tyranids I see an endless wave of gaunts with a few big uglys.
So what do you people think?