If you need a video converter for Mac that can handle just about every possible format then you can't go far wrong with Aiseesoft Video Converter for Mac.
Aiseesoft Video Converter for Mac supports a huge number of formats including AVI, MP4, MOV, MKV, WMV, DivX, XviD, MPEG-1/2, 3GP, 3G2, VOB and HD Video (TS, MTS, M2TS), MP3, AAC, and AC3 Audio etc. Not only that, but Aiseesoft Video Converter for Mac also extracts audio from video files and can convert on the fly to MP3, AC3, and AAC.
Aiseesoft Video Converter for Mac works with a huge range of portable devices including iPod touch, iPod nano, iPod classic, iPhone, Apple TV, PSP, Zune, Creative Zen Vision, Archos, iRiver, HP iPAQ, General Pocket PC, BlackBerry, Xbox360, PS3, YouTube and most major Mobile Phones.
Before conversion, you can perform a limited amount of editing. The video editor allows you to adjust output video effects, trim video/audio, crop video, add watermarks to video and merge video files into one output file. You have a certain amount of control over bitrate and file type when you output and you can preview before you finish. The general interface is a little too dark for my liking - the developers have chosen a very deep metallic blue which can make it a bit hard to distinguish certain features.
Overall however, courtesy of its many presets, Aiseesoft Video Converter for Mac will help you convert and crop video and audio with the minimum of fuss.