I have used and sold many knive brands, the spring assisted open blade is very popular, many knife makers now make some sort of it, Kershaw, Buck, Gerber , my pick of the lot would be the Kershaw Scallion 1620, it is slim , fits the pocket well has a removeable clip, and is much cheaper than may competitors of similar size , the blade holds its edge well, it is larger than its cousin the chive so it fits my hand better, the next step up would be the kershaw 1550 or the 1595 speed bump both which have a great handle shape although are much thicker and more bulky to carry.   The Gerber fast draw is another inexpencive auto, Buck offers many new autos , Rush, tempest, but price goes up quickly with these models