You're gonna get TONS of opinions, as always.
If you want the MOST reliable for self def get a revolver. S&W .38 special is a nice, easy carry.
If you want semi shoot the Glock 23, S&W M&P, Springfield XD9/XD40 sc, and Ruger SR9c/SR40c. I'd trust any of those with my life. Not that I wouldn't with a few others, but these 4, IMO, are the best starting point.