NO DRUG IS 100% SAFE sorry =(

however your best bet would be mushrooms

shrooms - the WORST thing that can happen to you no matter what is that you will throw up that has never happened to me and ive been doing them since i was 14 =)

salvia - safe

robotripping - REALLY REALLY REALLY EXTREMELY UNSAFE AND BAD =/

acid - ive heard bad storys i wouldnt do it but w/e

HWBR - safe if you know what your doing