1. Irregardless. When, exactly, did that become an actual word? You're using an additional syllable to say the same thing as "regardless."

2. Seen. I'm from the southern half of the United States, and too many of my fellow southerners tend to abuse this word to the effect of, "I seen Nancy down to the bank yestidy" rather than "I saw Nancy at the bank yesterday."

3. At the end of the day. Talk about a verbal crutch! "At the end of the day, we have to be more effective in our application of principles..." Uh, which day, exactly? STOP. DOING. THIS.