Any FO that's too floral, like rose, honeysuckle, etc. Last one that's put me off was honeysuckle from NG.
Pretty much most of the men's FOs - I don't even know what bothers me in them, but most of them smell like cheap men's perfume. Binned few batches made with Bay rum, etc. Just couldn't stand it or couldn't stand husband smelling like it haha.
Lavender - smells like toilet spray to me
BB Energy -makes me nauseous, it's just yuck. Binned a whole batch made with this FO, family liked it, but I just couldn't have it around. Strangely, Kumquat is similar as it's also fruity FO but I adore it, it's one of my faves.
Any FO with predominantly melon, cucumber or watermelon in it, can't stand it. Binned a whole batch made with cucumber, melon FO. It was vile.