Kryptonite gasoline/rocket fuel - even Clark couldn't save those vehicles if they went off-course, at least not up close. He'd have to try his vision/breath powers or do a Rube Goldberg-type thing.
Kryptonite lighting for camera flashes. They'd temporarily blind Clark.
redK stoplight "upgrades"! That would make for a fun episode. Would take him a while to figure it out, I think. In the meantime, Clark & Lois would kiss every time they got stuck at a light. Add greenK stoplight "upgrades" and that would be super-weird. Kiss! Get sick! Kiss! Get sick!
Kryptonite-based power, like Lex's bomb. If someone got Clark near that and hit him with lightning, he might lose his powers permanently or get killed (until a deus ex machina saves him).
To kill or at least seriously disable/injure Clark, Lex needs to seed clouds with green K to make:
Kryptonite rain.
Of course, he'd also have to get Clark outdoors when it pours.