Gnomes can be pickpocketed at level 75 Thieving; doing so yields 198.3 Thieving experience, and one of the items listed below. It is recommended not to pickpocket them until you have level 85 Thieving, because even with Ardougne cloak 3 and Gloves of Silence, you will fail most of the time.
A good method of pickpocketing is to pickpocket gnome women on the first floor of the Grand Tree by the banks on the west side. Corner a gnome woman just outside the bank, as this gives the benefit of the bank healing effect.
At level 85 Thieving (along with level 75 Agility), it is possible to steal double loot from gnomes. Level 95 Thieving (along with 85 Agility), is required to get triple loot. This can be good money for advanced thieves, earning up to 150,000 experience and 300,000 coins per hour.
A successful pickpocketing attempt will gain one of the following loot: