Question: What barcode scanners have been known to work with Koha?
Answer: The simple rule of thumb is, does it act like a keyboard device?, if so, it will work. (i.e. can you take the scanner, scan a barcode and have it show up in a text editor, if so, it will work.)
The main points to check are that it connects to your PC conveniently (can be USB or "keyboard wedge" which means it connects in line with the keyboard, which is useful with older computers), and that it scans the barcode type that you are using.
It is a good idea to test some 'used' barcodes if you have any, to see whether the scanner can read scuffed or slightly wrinkled ones successfully. Most scanners are capable of reading several barcode types - there are many, and the specification should list the ones it can read. You may need to adjust settings slightly, such as prefix and suffix characters, or whether you want to send an 'enter' character or not.
One more tip - some can be set 'always on' and may come with a stand, some have triggers under the handle, some have buttons on top, some are held like a pen. Think about the staff working with the hardware before choosing, as a button in the wrong place can be very awkward to use.
MS9590 VoyagerGS (more here: http://wiki.koha.org/doku.php?id=en:documentation:barcode_scanners:ms9590_voyagergs&s=barcode&s=scanner)
POS-X receipt printer
Star Micronics printer (exact model unknown) with a generic/plain text driver.
Star SP2000 (Nelsonville)
Star TSP-100 futurePRINT (Geauga)
"I know there have been a lot of questions on receipt printers so I thought I'd pass on my findings. We have been testing the Star TSP-100 futurePRINT. I found this print to be VERY easy to configure for Koha. I was even able to customize the print job by adding our system logo (a .gif) to the top of every receipt. Also with a bitmap created in Paint was able to add a message at the bottom of each receipt with the contact information, hours and website for the library that the materials were checked out at."
Epson TM 88 IIIP thermal receipt printers
1x1 labels using a Dymolabelwriter printer
Question: Are there any braille embosser or printer which has inbuilt braille converter and it is accessible with UNIX environment?
Answer: You may want to look into BRLTTY (http://www.emptech.info/product_details.php?ID=1232).