Tony Stark
The neck. Tony loved it when you would squirm when he would peck at your neck, and leave small hickeys. He did in public because he could do it secretly.
Steve Rogers
The forehead. Steve was so much taller then you that he loved just leaning down and pressing a soft kiss to your forehead, then murmuring how much he loves you.
Bruce Banner
The temple. Bruce loved pulling you into his side, and pressing his lips to your temple. Bruce just liked being close to you and he would always just pull you into him when he wanted to kiss you.
James Buchanan Barnes
The lips. Bucky would just hold your chin in his thumb and fore finger and press his lips to yours, then his hands would move to cup your face, pulling you into him. Bucky just liked showing everyone that you were his. And only his.
Clint Barton
The jaw. Clint just liked to kiss up your jaw and then press his lips to yours. He liked kissing your jaw because it light up a spark in you.
Loki Lauyfeson
The top of your head. Loki was a giant compared to you, and he liked pressing his lips to the top of your head, because it was the easiest place for him to reach.
Thor Odinson
The side of your head. Thor just enjoyed kissing you. He would always just bring you up to his height, and press his lips to the side of your head.
Sam Wilson
The under side of the ear. Sam would always just drag you into his lap, and kiss the under side of your ear. Then after pressing a kiss there, he would nip at it softly.
Pietro Maximoff
The palm. When you would cup his face in your hand, he would move his head so that his lips were on your palm. He would kiss your palm, and then slowly kiss your finger tips.
Peter Parker
The lips. Even though Peter was pretty shy when it came to PDA, right when his eyes looked at your lips, all thoughts of being shy went out the window, and he would just walk right up to you, and cup your face in his hands and press his lips to yours.