[Neferata]

I put "no, and i consider anyone who does so a cheater". Personally I dont think them to be cheaters, just unsportsman. I build my armies for Grand Tournament play, and I feel that if you're army is not built in such a way to handle a variety of situations, that you should suffer for your army's unbalances.

If both players pre-arrange a battle, on the other hand, then perhaps it would be more "fluffy" to tailor your army to counter theirs (no doubt they will do the same). But if you're just going to your local hobby store for friday night 40k, and you're stuck with a random opponent, I dont like playing against (nor do i like having to wait for) someone who makes up their army list at the last minute in order to build up a "hate-list" for my army.