What's the BEST SCREEN CAPTURE TOOL for SCREENSHOTS?

Hi, ive been trying to find a SIMPLE SMALL tool to take a screen shot of a movie trailer and i can't seem to find one. NOT VIDEO(like camstudio). I have tried vlc player and nero 7(nero is my main editing soft.) but the quality they give is horrible. I asked this guy what he uses
and he said intervideo windvd. I've looked it up and it seems like a very HEAVY LARGE program...i cant have that. Is there any SMALL app that will allow me to take HIGH RESOLUTION screenshots of trailers in there NATIVE SIZE(instead of resizing like nero). Thanks very much to those who help.