Almost every rental home we've lived in has had those ugly plastic outlet covers and switch plates. They're grooved and cracked, in pale beige plastic, and in the kitchen they are usually covered in more grime than we care to clean.
For less than $20 you can replace the 3-4 outlet plates in the kitchen with stainless steel plates from Home Depot or Lowe's. Screw the old ones off and put away somewhere for when you move out. (We always replace them and take our own plates with us.)
This is a tiny detail that many people don't realize they notice. But there's something really effective about it. The stainless steel plates are easier to clean, and they often lie flatter to the wall than the old plastic ones. We always feel like the kitchen has had a tiny upgrade; it's a little step closer to it being our own space.
Now, if we could just do something about our kitchen counters and our walls...
(Image: Faith Durand)