What tools do you use during pen-n-paper RPGs?

[Mr. Analog]

To be honest, as good as stuff like eTools (etc) are I find 3" by 5" cards work great as does a dry erase surface. In most cases I use the core books of a given system and I will often spend a day or more concocting adventure materials (mapping, designing traps, picking monsters or building foes for the players to fight). This way I get much more intimate with the details. I know more about monster / npc abilities when I have to pencil them in. I think the only other tool I use is the Encounter calculator, but that's because I'm lazy...

Ultimately the best tools are the ones that work.