Fred Merrygold is a fun one to annoy as he'll write some passive-aggressive articles afterwards. Twinkle Thwaites is also fun, but she writes for Witch Weekly and is more interested in what people wear and whom they might be dating, so she doesn't count for this.
The ones you should avoid teasing, on the other hand, are Pennyfeather from Quaffle Waffle and Rita Skeeter. The first one is a decent chap, and the latter is a vindictive old hag.