ESD sensitivity of MOSFET pins
If you exceed the Vgs voltage given in the datasheet, you can blow through the gate insulation layer. You will never feel 200V of static charge, but it will ruin a MOSFET. As Respawn pointed out, they are not as sensitive after being soldered in because there are other places for charges to go besides right through the FET.

If you're going to be working with stuff like this a lot, you'll probably want to set up an anti-static mat, get a wrist strap, and reduce influence from carpet and clothing while you're building the PCBs.

And always transport your boards in metallized mylar bags!