Heat remover - A wall that cools down particles to room temperature then generates a spark. If the particle that passes through is cooler than room temperature, then nothing will happen.
Mixing of lava - two types of lava (example BRMT and BGLA) will mix. As of 43 Beta 0, The positions of BRMT and BGLA after cooling from lava is so much the same.
down solid - position of particle moves down one pixel at a time (or maybe faster) if a particle is sitting above it. This is not a falling solid, because the movement is by particle. (This is like a one-particle elevator)
up solid - pretty much the same as down solid, but the movement is upward
I will not suggest left and right solid.
reverse solid - the direction of the up and down solid reverses when touched by this. (the up becomes down and down becomes up)
half-screen mode - what you do on one side happens to the other side (does not include stickman).
I would like to see the addition of hydrogen. Hydrogen+Oxygen=Water. This could be useful because I once tried to make a nuclear reactor with a working water cooler. I used the fan to proppel the water through the tube the reactor core. This did not work well because the water would often clog up the pipe, because if I increased the fan strength, it would mess with the main reactor. Using the gasses would be good because I could set the fan strengh to a lower level and the hydrogen would mix with the oxygen in the main chamber, thus elimintate the problem of pipe blockage.