D-roy raises, around :47 here:
Kind of a bent over one-arm chest fly. Seems weird and you'll "only" use about 5 pounds, but it's all
pec contraction. Try it at the start of your chest session.
For biceps and a few other bodyparts, I really like using touch training. Simply touching the fingertips of one hand to the working muscle. Seems obvious but it's underutilized. So with one-arm dumbbell curls, I'll be curling with the left arm and have the fingers of my right hand touching the left biceps during each rep.
Same for one-arm lateral raises and rear delt flyes, one-arm pulldowns or cable crossovers, standing leg curls, seated calves, basically anytime you can reach the working muscle with the non-working hand.