What are the best first foods for babies?

Very interesting question.
We all understand that first food should be nutritious and easy to digest. Interesting thing is that we will be getting very diverse responses to your question because first foods are mostly influenced by the type of food being eaten in that region. Genes 2 Teens is a global parents’ community and I am very keen to learn what first foods parents prefer from different parts of the world.
I remember when I was looking for good food choices for my first born, a very dear senior colleague (who was a pediatrician) said to me that if you daily eat cake then select packaged food, if not introduce your kid to real food being eaten around them. This has been the guiding principle for me when it comes to weaning.
Few first foods that my kids enjoyed included mashed bananas, boiled potatoes, boiled eggs, rice pudding (made with rice flour and milk), Khichri (white rice cooked into a thick paste with lentils and salt – I sometimes also added boiled and grinded chicken to it) and Semolina pudding (semolina, ghee and milk cooked into a paste). I always tried to create a balance between sweet and savory foods so kids could develop taste for both.
These are few first food ideas from me, a mom living in Pakistan. I am following this question to see what mothers from other areas use as first food.

I am very much into baby led weaning. My babies ate whatever we ate (within reason) and I made sure to cut it up into safe pieces for them. It was the easiest way to feed them without needing to create an entirely different menu for the baby.

It's not for everyone, though. There are some tried-and-true items that all my kids loved.

2 ingredient banana pancakes (1 banana, 1 egg)...also leaves room for adding things like oats, hemp seeds, flaxmeal, etc.

Steamed vegetables like beans are great. And other ones that you can cut into the same shape (carrots and squash for example).

Rice and beans are small enough for them, but just a heads up - it gets messy if they do it themselves!

And a one-year-old may be close to using a regular cup, with a straw even, and then you can make them smoothies. Smoothies are wonderful for babies.

I also really love making healthy muffins that the whole family can eat. Reducing or using a sugar substitute like applesauce or maple syrup helps keep the sugar level low for littles.

It's been a while since my girls were little ones, but I think there are some common first foods which stand the test of time.

Introducing a wide variety of foods early on in development can encourage less picky eating and begin to provide kids with the daily nutrients they require.

Avocados and soft fruits are both easy to digest and full of vitamins and minerals. Their various shapes, some when cut up, also help encourage a child's growing dexterity. Fruits like bananas, strawberries, mango, and peaches are good starter fruits, just be sure to cut into appropriate-sized pieces, or adding them to a smoothie is also an option.

Oatmeal is another great option, as it helps your child begin to work on their chewing skills. Add some pureed fruits, a bit of honey (which can be introduced at 1 years old), and it's a fibre-rich, nutritional offering.

Eggs can be introduced at this age, although I would say to serve these separately from other foods and see if there are any adverse reactions, since it can be an allergy-prone food for kids. Served scrambled or hard-boiled, in appropriate-sized pieces.

And you can start introducing chicken, turkey, or tofu. For the poultry, it's better to poach it first, then purree it with a small amount of yogurt, until better chewing habits are established. Also, don't season it, let the natural flavors be introduced.

For tofu, which neither of my girls would eat as cubed portions, can be blended into smoothies, in its silken variety. Sneaky and nutritional!

I think one of the biggest things I did with my girls which helped them establish good eating habits was to keep their sugar intake to a bare minimum. Even if a Sweetener was used, it was a natural one, like honey, agave, or maple syrup.