Top recommended scanner:

Fujitsu ScanSnap S1500/Fujitsu ScanSnap iX500

The ScanSnap S1500 is technically no longer available, having been replaced by the newer ScanSnap iX500, but those of you who own them and nominated them noted that both models are exceptional at quickly scanning documents of different sizes and shapes, and even converting some text documents into searchable PDFs. While the S1500 was Windows only, the iX500 extends support to Mac users who want to organize their lives too. The S1500 sported 20ppm scanning, and the iX500 brought that up to 25, and both models have a document feeder that makes scanning multi-page documents as easy as loading the tray—no feeding each page one after the other. The iX500 also supports scanning to iOS and Android devices, can make PDFs with one button, and more. It'll set you back $500 retail ($430 at Amazon).

Making PDFs with one button is super useful.

See the review for the other four recommended scanners.