Well, it looks like more people are trying to level pacifists, now that it's quite a bit easier with herbalism and mining XP and Archaeology, so it might be a good time to recap all the obscure ways you can get credits for a kill...
First, of course, grouping with anyone who kills anything counts as a kill. Even getting a portal from a mage can give you a kill if he zaps something while you're grouped.
Second, the tagging rules (a mob "tagged" by you will count as your kill even if someone else kills it) are not always obvious, and they have changed in the past. I think now, any action that draws aggro (except for proximity aggro) can tag a mob, not just damage, so using any non-damage spell like fear or sleep can tag a mob as yours, so you can only use these safely when in an instance.
Third, some things count as kills that aren't obvious; removing NPCs trapped by webbing counts as killing the web, for example, and destroying a nest in the Throwing Down quest in Northrend also counts as a kill by itself. And if the Headless Horseman sets you on fire during the burning town event, if you kill a low-level player or critter because of the fire coming off you, it counts as YOUR kill. Oddly enough, the Absorbent quest in Azshara doesn't count as a kill if a water elemental is killed by your aura. Other quests where you destroy something might or might not count, so if you can, try it with another toon first.
Forth, with a lot of tiny critters running around, try to get into the habit of gathering items behind you; you can gather, but not attack this way, so it reduces the chance of an accident.