Substitute and shed tail prevent flinching. Other ways to completely prevent fake out from hitting include protect and double team. Some abilities prevent fake out under super situational situations, like volt absorb when fake out is used with galvanize, soundproof when fake out is used with liquid voice, and telepathy when fake out is used on an ally. Moving before the fake out also prevents flinching. Several moves have higher priority, like helping hand, and technically you don't flinch when you switch in.
Also Amethyst became number 1 by answering and commenting on thousands of questions. Of course he/she/they/it would comment on your question. This site rewards activity and contributions, not being mysterious or whatever.