So here's what I suggest: if you love someone, tell them so. If someone has done something nice, say thanks. If someone deserves something nice (or even if you just suspect they may one day perhaps deserve it, if you're brooding or cynical at the moment) then do something nice for them. And if you've hurt someone (and what the hell did you think this post was about?) say sorry. Even if you're not in the depths of a Northern Hemisphere Winter.
So pick from this list whatever you like. I'm sorry. I don't know about nice, but here's a Bawdy 1970s Hospital. I may not say it to your face, but I do love you. And thanks!