Pour moi:
1) Kiss scenes
Really any kind of physical intimacy, from hugs to handshakes. I go to draw it once in a blue moon, and suddenly realize that I have no muscle memory for it, like "good god I've never done this before...how can this be??"
It's just strange to me...I do kinda avoid romance in my own stories, but I write tons of it in fan content, so you'd think I would draw some once in a while, just for fun. =/ And there's really no explanation for the lack of more platonic contact...it's like my characters just somehow never touch each other, and it kinda freaks me out...
2) Food
I mentioned this once before on this forum...I love food, but I almost never draw it and it's such a shame...there are so many techniques I'd like to try...! >_<
3) Electronics
Sure, I draw phones occasionally, but anything else? A laptop? A TV? A radio? I've simply...never. I have no idea why.
From this (taking into consideration that I've spent years drawing comics...) you could surmise that most of my characters are antagonistic fantasy aliens who do not live in the modern world, or are otherwise confined to highly specific environments (e.g. schools)...and you would not be very far off base. :9