As of late 2024, OpenAI has two primary models that represent the cutting edge of their technology, depending on the use case:

**1. GPT-4o (The General-Purpose Flagship)**
Released in May 2024, **GPT-4o** ("o" stands for "omni") is OpenAI's primary flagship model for everyday use. It is a highly efficient, natively multimodal model, meaning it can process and generate text, audio, and images seamlessly in real-time. It is the default engine for ChatGPT Plus and free users, known for its speed and natural conversational abilities (especially in voice mode).

**2. OpenAI o1 (The Advanced Reasoning Flagship)**
Introduced in September 2024, the **OpenAI o1** series (currently available as *o1-preview* and *o1-mini*) is their newest breakthrough in artificial intelligence. Unlike GPT-4o, the o1 models are designed to "think" before they answer. They use chain-of-thought reasoning to tackle highly complex problems in math, coding, and science. 

**Summary:** 
If you are looking for the fastest, most versatile multimodal model, the flagship is **GPT-4o**. If you are looking for the absolute latest model built for deep reasoning and complex problem-solving, it is **OpenAI o1**.
