Truglo TFX or TFO. TRUGLO(R) | Firearms | Handgun I just put the TFOs on my Shield and am very happy with them. Both the TFX and TFO are a combination Tritium/fiber optic sight, highly visible day or night. I have the Trijicon tritium night sights on my FS M&P9, and if you have trouble seeing regular white dot sights in the daytime, you will likely fare worse with the Trijicons..
I have Trijicon HD XR's on my 3.6 and the bright orange outlined front sight makes it easy to acquire your target. The XR's have a thinner front sight blade to make more precise hits at longer distances.