Q: I failed my geometry class for one grading period, but I am a straight A student for everything else. Is there any way for me to get accepted by a pretty good college?
A: Short answer: Yes.
Longer answer: Sounds like you had a tough time with your math class, but you are a hard-working student and this failure came as a real shock; failing is not what you ordinarily do. And someone is telling you, "Now, you'll never get into a good college!" Take a deep breath. Everyone messes up on something. But if this one grading period's failure is uncharacteristic, and everything else is fine, you will have no problem getting into a ton of colleges. You may run into a problem, however, if this is part of a pattern of weak grades. (As a side note, remember that you still have time to improve your grade before the end of the semester. Ask your teacher for help!)
Other than the most selective of selective colleges (the ones accepting 10 percent or fewer of applicants), admissions readers look at the "big picture". If your big picture is good, you will be fine. The big picture includes: What is your overall academic achievement? Have you taken challenging classes? Are you generally a good student? Do you devote a portion of your time and effort to your school and community? Do you have some focused interests? Do your teachers have good things to say about you?
In terms of the big picture, many applicants with a couple of Bs and even a C are more desirable to some colleges than those with straight As. If the straight As come at the price of sacrificing time for sports or music or art or service, it's not worth it. Students are whole people, not just a collection of GPAs.
Now to the other part of your question: can you still get into "a pretty good college"? Exactly what is "a pretty good college"? It doesn't have a specific name. It's a place that is great for you, where you can thrive. It's a place where the faculty cares about its students, tries to impart the joy of learning, and enables student to think and do research independently. A good college is one where you will learn from other students, too, because there is a vibrant classroom atmosphere, and people are not afraid of asking questions. PLEASE do not go by magazine rankings or full-color advertisements. There are hundreds of excellent colleges and universities in this country. Do your research, and you will find them!