A number of years ago, I had the opportunity to take what I wanted from my Great Uncle George Close's exceedingly diverse fly tying collection after he passed away. I didn't take much; a pair of scissors and a few books. But the real prize were his favorite scissors, not because they were worth a lot of money or overly special except for being quite personal. To me, there is nothing more personal to the fly tyer than their scissors - be they cheapos, some really expensive pair, or something in-between.
In my mind, scissors are the tyer's greatest connection to their craft. Like most other experienced tyers, mine are in my hand ALL THE TIME. I learned to hold my scissors in my bobbin hand from George. I learned that Thompson Ice Scissors were his favorite brand 30 years ago and I've used a pair or two myself. Since then, I've learned that scissors are a great tool but for me, many different tools work just fine. I'm not much for having them sharpened, particularly the serrated edges so I buy relatively cheap and assume they'll last a few years, particularly if I don't abuse them by cutting tough things near their tips.
I am not a stickler for a brand - I've used many over the years. I've switched brands and configurations. Today, my favorite pair are the Loon 3.5 or 4 inch models or an exceedingly inexpensive pair of Fiskars scissors. Seriously, do not over look the sub-$10 pair of Fiskars. Last year, they were something else. George's last scissors were a pair of Thompson Ice Scissors - a favorite of mine. For years, I had used the Anvil Ice scissors with the adjustable handles but over time, I find them to get out of configuration too easily and are too hard to get back into alignment. So I've moved on to other, sturdier configurations.
Each scissors has their application. Of the ones above, three of them are "all purpose" scissors and the Dr. Slick's to the left are a fine tipped scissors that are great for clipping a stray hair or hackle fiber here and there. I would say that I tend to use three different scissors types - the all purpose scissors like most of those above and my cheapo Fiskars, a fine tipped pair get used once and again to clip a stray fiber or hair, and a deer hair pair get used on larger flies and for cutting tougher materials.
Anvil Ice Scissors and many other with adjustable handles are great and they'll last a few years but I find over time, they get out of alignment and are tough to get back into alignment. The handles above show how they have been bent so the tips are difficult to get into alignment again. Though, I would say that these scissors provided a number of years of use.
These Loon Outdoors scissors are my current most used pair - other than the ultra-cheapo Fiskars. A good pair of adjustable all-purpose scissors is a great default pair of scissors for any tyer. There are a great number of options.
Fiskars "Classic" Precision Straight Scissors 10 cm or my slightly more expensive Loon Razon Scissors (4 inches) are what are typically in my hand when tying. I have no idea how long the Fiskars will work but I know a great many tyers much better than myself that are Fiskars fans.
I've always been in the relatively cheap works just fine camp. I like a pair with at least 1 serrated edge as I find they cut some of the slippery fly tying materials (like gel-spun poly thread) better than smooth blades. Whatever scissors you like; hold them close and use them often. Cheers!