I am a letter.
I am in talk, and in stop, I am in tickle, and in tackle, I am in bullet, and kite, I am in poster, and in tear, I am in torn, and in fear, I am in tick, and in stock, I am in tulip, but I'm also in by.
What am I?
The question doesn't specifically ask for a letter for an answer. So I am going to say as it said its just a letter. Also couldn't find a common letter among those words. Though 't' is repeated in almost all except 2.
I am a letter
the letter is T
I am a creature that makes you go "Ick!" I can literally stop you dead in your tracks. I'll come out of nowhere and I'll get you quick. My bite hurts as much as stepping on tacks. I'm one of the most dangerous desert creatures of all. People get scared when they see me crawl. What kind of creature am I?
Almost all I do is talk and sing. People love me and take me with them everywhere. I reach people all around the world and tell them what they want. They rely on me for everything and I can even save their life and yet I don't have a mouth. What am I?
I come in many shapes and sizes, many colors, and I stick to many surfaces but I am, in fact, not sticky at all. What am I?
For some, I am used to get around. I never even touch the ground. Sometimes I fall in a large open tank and sometimes I float in the air and then rise. What am I?