Can someone suggest me please?
I never bought laptop with such goal but...
If I was looking for a laptop expecificaly for that, I would had a few specs in mind:
Sorry, grammar nazi here, but instead of "expecificaly", It should be either "specifically" or "explicitly". :D
yeah how much grammer have you learnt..grammer nazi
thank you for suggesting me the requirements and i i have heard that thinkpad is good for pentesting,is it?
and jansen can you suggest me best usb dongles because i am thinking to buy it with my laptop.
I can't help you choose the best dongles because it depends on the brand and the chipset. You should begin with: http://www.aircrack-ng.org/doku.php?id=compatibility_drivers
I use a few but let me tel you the best buy I did so far was this http://www.dx.com/p/netsys-9000wn-6800mw-802-11b-g-n-150mbps-usb-2-0-wireless-network-adapter-white-123377#.Vau4dPlVhHw
Allows macchange, monitor mode and packet injection (I think, I haven't done for a while). But for you intent maybe is not the best choise.
Bottom line is, check the market and see whats available and what fits your budget, after that check the chipset, if it permits to do what its needed for (monitor mode, packet injection...) and for last try to check some reviews (mainly what concerns range).
Insted of looking up good laptops if your stumped look up mobile workstations, Their generally more expensive but that got a lot of gas in them, try to find one on sale and it'll do pretty damn good