The fullest exploitation of Howling Mine was implemented in the first Pro Tour by Mark Justice
Few cards are as flexible as this amazing 2-drop, and it always comes in handy
This is mainly because it creates a pseudo-chaos state where players switch control of it each turn
(Choose a creature with the least toughness among creatures you control and put a +1/+1 counter on it.) With heat, sand can form a delicate work of art
Cheatyface can be snuck in at any time, while the Armchair is limited to your turn, but both must be in your hand to work
You can also go down the pod or toolbox route, finding permanents with powerful enter the battlefield abilities for any situation, whether its Eternal Witness, Noxious Gearhulk or Aether Channeler to name but three