Which is the best colon cleanser in the market?

They're not necessary, but if it would make you feel better, and they often do temporarily because they do pretty much what a better diet would be doing, here's a list of some of the more popular ones with reviews: colon cleansers (http://www.naturalhealingtoday.com/colon_cleanse_product_reviews.html)

You'd be better off in the long run, as there is no quick fix, by putting your money into eating a well balanced diet (plenty of fruits and veggies), limit processed foods, increase daily fiber, and be sure to have adequate amounts of fluids. Not once in awhile, but on a regular basis.