Literally anything with a hard edge is a bottle opener, other bottles (most often), lighter, a coin, keys, a drinking glass, a rolled up and folded bank note/ reciept/ anything, a pair of jeans scrunched up, a knife (common in the kitchen), a frozen chicken, tv remote.
I can't honestly remember the last time I used a bottle opener, I tend to grab something hard and open with that.
You need a strong grip to be able to do it with smaller objects like coins or keys but overall it's all about leverage, hold the bottle by the neck firmly, grasp your hard object in your hand and place under the lid then push against your hand gripping the neck to lever the top of the bottle off.
If you have wimpy little hands it'll hurt by the way, take up piano or bass or something, you'll get a grip like a vice.