Like previous games, several Pokémon have the Pickup Ability. This Ability allows for the Pokémon to randomly pick up items. The items vary based upon the level of the Pokémon. However, HeartGold & SoulSilver have their own PickUp list. First, below are the Pokémon that can have the PickUp ability.

Meowth Aipom Teddiursa Phanpy Zigzagoon
 
Linoone Pachirisu Ambipom Munchlax  
 

Now, each set of Levels have varying items, with some items being rare for the lower levels but common for the higher levels. Hover over the items for their name:

Lv. Common Uncommon V. Unc. Rare V. Rare
1 - 10
11 - 20
21 - 30
31 - 40
41 - 50
51 - 60
61 - 70
71 - 80
81 - 90
91 - 100