Here's a complete list from several EMG measurements (for whats worth it). Those declines give me a much better stretch & contraction compared to flat bench movements.
IEMG max motor-unit activation
Exercise
%IEMG max
Pectoralis major
Decline dumbbell bench press
93
Decline bench press (Olympic bar)
89
Push-ups between benches
88
Flat dumbbell bench press
87
Flat bench press (Olympic bar)
85
Flat dumbbell flys
84
Pectoralis minor
Incline dumbbell bench press
91
Incline bench press (Olympic bar)
85
Incline dumbbell flys
83
Incline bench press (Smith machine)
81
Medial deltoids
Incline dumbbell side laterals
66
Standing dumbbell side laterals
63
Seated dumbbell side laterals
62
Cable side laterals
47
Posterior deltoids
Standing dumbbell bent laterals
85
Seated dumbbell bent laterals
83
Standing cable bent laterals
77
Anterior deltoids
Seated front dumbbell press
79
Standing front dumbbell raises
73
Seated front barbell press
61
Biceps brachii (long head)
Biceps preacher curls (Olympic bar)
90
Incline seated dumbbell curls (alternate)
88
Standing biceps curls (Olympic bar/narrow grip)
86
Standing dumbbell curls (alternate)
84
Concentration dumbbell curls
80
Standing biceps curls (Olympic bar/wide grip)
63
Standing E-Z biceps curls (wide grip)
61
Triceps brachii (outer head)
Decline triceps extensions (Olympic bar)
92
Triceps pressdowns (angled bar)
90
Triceps dip between benches
87
One-arm cable triceps extensions (reverse grip)
85
Overhead rope triceps extensions
84
Seated one-arm dumbbell triceps extensions (neutral grip)
82
Close-grip bench press (Olympic bar)
72
Latissimus dorsi
Bent-over barbell rows
93
One-arm dumbbell rows (alternate)
91
T-bar rows
89
Lat pulldowns to the front
86
Seated pulley rows
83
Rectus femoris (quadriceps)
Safety squats (90 degree angle, shoulder-width stance)
88
Seated leg extensions (toes straight)
86
Hack Squats (90 degree angle, shoulder-width stance)
78
Leg press (110 degree angle)
76
Smith machine squats (90 degree angle, shoulder-width stance)
60
Biceps femoris (hamstring)
Standing leg curls
82
Lying leg curls
71
Seated leg curls
58
Modified hamstring deadlifts
56
Semitendinosus (hamstring)
Seated leg curls
88
Standing leg curls
79
Lying leg curls
70
Modified hamstring deadlifts
63
Gastrocnemius (calf muscle)
Donkey calf raises
80
Standing one-leg calf raises
79
Standing two-leg calf raises
68
Seated calf raises
61
