I like the Ergonomic cutter by Olfa. It retracts the blade when you let go of the handle. The other ones leave the blade exposed and you have to remember to push it back. Easy to get yourself cut.
My favorite rulers are the Olfa rulers with the yellow and black lines. I have the square set from Joanne. Bought it with a 50% coupon. I also like some rectangular rulers as well.
Recently I bought a magnetic pin cushion with a cover. That way I can put the cover on and take it with me to classes. The pins I like the most are the long, thin, glass-head ones.
For my machine, I got a bendable light to attach to the side. That really helps with visibility at the needle.
While I don't necessarily believe in one-trick pony rulers, I do use the Easy Angle and Companion Angle ruler a lot and I got the Tri-rec ruler too.