At the risk of sounding like a Grammar Nazi, there are three things that really bug me.
People who write "lightening" when what they really mean is "lightning," as in "Dr. Frankenstein brought the monster to life with lightning!" He didn't lighten the monster, FFS, nor did he apply makeup to do some "lightening" of the monster's complexion. He fucking zapped that shit! With LIGHTNING!
Abuse of the apostrophe-S. I kid you not, I once saw a a handy-man type of company have an otherwise very professionally made, professional-looking logo on their van and storefront sign that said something to the effect of "We do timely and professional repair's!" Fuck, if you can't even use an apostrophe-S properly, why do you think I'm going to trust you to wire my home, or fix my plumbing, or anything else?!
And finally (and I don't know why, but it fills me with rage), is seeing a backwards ampersand. It looks like this: & it points rightwards, and that's the fucking way it should point, and if you point it left (backwards) I will think you're a fucking moron! I know there are some artsy ampersands, but I mean regular ones. Worst Offender Award goes to those lit-up rectangular signs where the letters are printed on clear plastic panels, the kind you see outside the VFW or bars or gas stations or quicky-stop markets in small towns. Now okay, I know the "R" in "Toys R' Us" is backwards, but that's okay because it's meant to be a store for kids so it's cute and denotes it's for kids. I feel no rage when I see a Toys R' Us sign, maybe only at their prices. But an ampersand points to the right because it's fucking supposed to, goddammit!