I know that Lesche are the best plug cutting tool... But I want to mention that Friskars Big Grip Multi-Purpose Planting tool is a good runner up for beginner.
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Like the Lesche, it has tooths one one side and it is sharpen on the other side (I re-sharpen mine). It has aV groove that can be used to cut small roots with a little tap on the handle. The shape of the blade make it a very strong tool and it is able to pry a plug out of the hole without worries.
http://www.fiskars.ca/Products/Yard-...-Planting-Tool
The price, 8.95$ CND at Canadian Tire ...For the beginers on a budget
Daniel <