Playing big games, it sometimes gets hard to remember that there is a nemesis bonus to add in. It would be great to have a tangible marker.
I use some home brewed cards that I made for just such a thing. I still forget 
Does Spiff’s accessories include nemesis markers? I can’t remember.
They do. The file that has little 3D tokens for things that need remembering (+ damage, damage resistance, etc.) has one with a skull which can be used to indicate nemeses.
Here's some tokens I use, I put them on some posterboard that matches the thickness of the official tokens.
http://www.mediafire.com/view/d2a39qfkjrx0r2g/nemesis_tokens.pdf
I almost never use the nemesis bonus at all, so it's never really forgotten. I might be in the minority there.
I just use a +1 damage token, but keep it on the bottom of my character card, while i have all other markers at the top.
I just use extra gems and things like that, and I'll drop one in the appropriate HP pools to remind me whenever I take anything out that there's something else to keep in mind (like nemesis bonus). I'll generally try to use something appropriate (like red gems for nemesis).