Dremel 7700
I have used corded Dremels for years as a household tool, and found the quality of the brand to be outstanding. After trying a number of grinders marketed and sold in pet stores and finding them to be useless on the thick nails of my big dog, it was a no-brainer to look to Dremel instead. I wanted a cordless for nails, as I didn’t want to scrabble a power cord through four furry legs or coax my dog into a specific location near an outlet every time it was time for a trim. Plus, it would be awful to accidentally nick a quick and have him bolt, only to get tangled in a cord, or have an operating power tool go flying in the process. The first 7700 I purchased worked well for a few months, then the battery became loose and would fall off during operation. I also found that the unit lacked power, likely related to a poor battery connection. I complained to Dremel and they offered to send me a new battery immediately. They didn’t send just a new battery, but rather a whole new 7700. I’ve been using the new model for 8 months now with zero problems. I am so impressed with their response to my complaint that I am now a life-long devotee. All future rotary tools will be a Dremel, no question.
A good video for trimming information: https://www.youtube.com/watch?v=7cq5X8aV95E
For further information on the tool: https://www.dremel.com/en_US/tools/-/search-tools/find-by-category/27343/rotary