My favorite would be the frog oil jars. I also like dropping paper bombs on top of the makibishi spikes. If you drop it and then switch to a different part of the stage, the bomb will go off without the countdown, while you are safe.
but you have to drop the paper bombs from the air or else they will blow up immediatly. i like the explosive seal (bomb seal, whatever), frog oil, and i guess the demon wind shuriken (i will use those for a while, i did the last mission like 60 something times and i have 99 of the demon wind shurikens).