The simplest most amazing thing I love doing with a guy is cuddling up with him.
More specifically, I love being the big spoon, the one to hold you in my arms. Yes, I'm a little guy, and a sub, and a bottom, and I really really love being held and a guy wrapping his arrms around me as he gets into bed (and feeling his cock against my ass :P), but honestly, there is no greater, simpler pleasure for me in life, than having a guy fall asleep with his head on my lap, or curling up against me as we watch movies, or letting me hold him in bed, to be the one that gets to effectively say "you are mine to protect, and i will always do that for you". And maybe the size thing is something to do with it, that a guy a foot or so taller than me will feel so comfortable with me, that he trusts me so much, he'll go okay you're small, okay i might choke half the life out of you as i fuck your ass, but now, in this moment, you get to be the one that takes care of the other in the relationship.
It's definitely a sign of trust and affection on my part. I hate people leaning on me, falling asleep on me. It's a childhood neurosis thing, being small people always use me as rests and it pisses the hell out of me. For the guys i really care about, i'll let you rest your head on my shoulder, and fall asleep on me, because i'm happy just to be with you, and any amount of mental irritation, or physical discomfort when my arm inevitably goes dead, is worth it for those boys.
There are many things that make me smile in the world, and there are all sorts of things that I enjoy, but this is the simplest thing, that will have me grinning the entire time whilst it's happening. I love it and it's important to recognise the little things.