Honestly, I don't fare much for PvP, but I still strongly support it.
It gives you the upbeat fear that you could drop at any minute.
Plus, I like a good game of cat and mouse, while I play as the mouse.
But, on topic, traps. Lovely things.
Honestly, you can't go wrong with redstone. (Well, sure you can, but I meant hypothetically.)
With redstone, you can go from minor pitfall traps, to a complex locking mechanism that will throw you into a different room if you get the wrong combination.
Let me just say, the best traps are usually made of redstone.
But, in all honesty, I'm terrible at PvP. Which is why I adore traps and running tactics.