I have been flying with my DD since she was 5 weeks old. When she was an infant, I found that the most useful item to have on the plane was a baby carrier so I could have her attached to my body and not have to attempt to hold her once the plane was in the air (Ergo & Moby Wrap were my personal favorites).
As she go older, I would always pack a carry-on back pack full of toys (old favorites and new treasures) to attempt to entertain her. I would pack triangle crayons, snacks, finger puppets, cars, books, dolls... just about anything smaller than my fist but not a choking hazard that I could think of. I was always way over prepared. Generally, the only thing she would want to play with on the plane was whatever electronic device I had brought to entertain myself (phone or tablet). I would land and find that a majority of the items I had brought for her remained untouched since she would pass the time playing games on my phone/tablet.
One trip, I tried wrapping all the small items I brought for her in tissue paper (she was about 2 years old at the time). I had heard that the unwrapping was a fun distraction and she would enjoy playing with all the toys as she unwrapped them. Well, the unwrapping was fun for her...but that was all she wanted to do. Unwrap and then ask for more things to unwrap. She unwrapped about half of the items that I brought and then was ready to settle in with the tablet and watch a movie on it... Of course that did leave the other half of the toys to unwrap on the way home.

So after 4 years of lugging a heavy carry on bag full of crap toys that she barely touches, I have simplified my life and now just bring a pair of child sized headphones for her to plug in and enjoy her movies/games, which she has basically been doing since she was 18 months old.
I have to brag and say that I have received numerous compliments on how well behaved she always is when we fly. Often, we stand up to disembark and the passengers in front of/behind us are surprised to see that there was a child sitting in the row that they hadn't even noticed.
Here are my favorite child friendly flying tips that have worked for us:
-Let your child have free reign at the airport. They need to run around and get all that energy out BEFORE getting on the plane. I encourage my daughter to run (yes, we do run) in the airport. I would avoid strapping her into a stroller prior to getting on a plane at all costs!
-I make sure she understands that she needs to get her "screams" out before we get on the plane. This is something we have been doing since she was 1. Before entering a building (plane/car) we stop at the door way and get our screams out. It has worked amazingly well! I will add that there was a time period of training where we would immediately vacate any building we were in if she ever started to scream. It was especially effective because it happened to be winter when she was going through this screaming phase so we would stand out in the freezing cold together and return once the screaming ceased.
-If your toddler gets antsy on the plane, get up and take a walk with them. It drives me crazy when parents won't let their child get out of the seat and just sit there while the child screams. Of course, I understand that sometimes the "seatbelt" light may be on and you can't get up. But I have never been on a flight with the seatbelt light on the entire time (maybe I'm just lucky). I find that there are often friendly strangers that are more than happy to wave

and smile at a happy toddler walking down the aisle which is a great distraction for an antsy child.
-We typically fly on Southwest so we are able choose our seats as we board. I try to seat my daughter behind a child so that on the rare occasion that she does kick the seat in front of her, she is less likely to anger a stranger.
I hope I am not coming across as being too preachy on the subject. I know you were only asking about toys but these are a few tips that I have found through experience (and from others' suggestions) that have been the most helpful for me and my daughter. Best of luck to you on your flight... and remember, you can always buy a few drinks for your neighboring passengers to make the ride more enjoyable if you (or your child) are having a difficult flight.