Me, I use IrfanView 4.0. It's free, fast, easy to use, and has options for cropping and simple editing. As for viewing comics, I use ComicsViewer - It's pretty comfortable to read comics with it and it has many options like ZIP/RAR viewing and auto width.
I don't find Windows Picture and Fax Viewer & ACDSee very good. It's slow to load on my computer and don't have very much options. Try IrfanView. It had some powerful features too like batch processing and has plugins for opening bunch of other file formats (not just pics). You won't regret it. http://www.irfanview.com/ It's a freeware and very small to download. No piracy worries ;D
I used to use Irfanview, but when I started collecting high-resolution pornography I found it was very awkward to cycle through the images using the arrow keys. So now I use the default Win7 viewer.
Same here-its OK on preview,but if I double click on it,takes 2 minutes to load that Media Centre shite,and 3 minutes to close it.....
I used to go with Windows' integrated viewer, but as he can't play animated gifs and other formats, i'm now using XnView. I tried IrfanView but it had a strange behavior on my system.