Here are some stuffs that I think easy in PvZ2.

1. A-noob-is (Anubis) achievement

I think this is VERY easy if you quickly use Plant food on Peashooters / Repeaters that are in the same lane as the Tomb Raider Zombie.

2. Gargs

Gargs are pretty easy to kill with about 3 plant foods used on the Repearter when attacking Gargantuar, though it wastes your plant food

3. Multiple Buckethead ZOmbies

They can be easily be defeated with some instant kils and Plant food (of course)