When I started technician work, I was scared of a large centrifuge with a very heavy and very expensive rotor, liquid N2 (no because of the potential injury so much as getting growled at for using it wrongly), the freezers (in case I accidentally thawed other people's samples), any strong acids or alkalis, anything radioactive, a histamine autoanalysis machine we had, and a large water purification machine. Pretty much everything then...
A few months later, and I was steadier, and by the time I finishe,d nine months later, I was as confident as you can be.