You said 'tactical' but do you simply mean a high output light for EDC (every day carry) or do you need a light to coincide with a CCW?
If you simply want a strong performing, comfortable to carry light that is comparable to the 6Z/ZP and the X5's performance I'd highly recommend the Surefire Executive series lights such as the E2E-HA or E2D Defender -
The E2 series lights are ideal for EDC because of they're smaller, slimmer design, they the pocket clip, a clicker style tailcap and you have the option of switching to an LED head that's roughly the same size as the std. head. The E2D Defender has the strike bezel design and is certainly intended to be a defensive tool. The E2E-HA & E2D have 60 lumens performance and an approx. 75 min. runtime.
If you're after the combat grip design lights then the G2Z is certainly a winner, and I would recommend it over the Z2 based on it being a little more resiliant if dropped, won't show routine wear as bad and is slightly less expensive. There is another choice that might be of interest though, the C2 Centurion has both the combat grip design and has a pocket clip for easy carry and quick deployment. Here are couple pics of it -
C2-HA -
C2-BK & E2D (w/ Z61 clickie t/c) -
If those are more than you want and are just after something bright then the SF G2, 6P & 9P are econo choices. The PentagonLights are great and the HA finish variant are very affordable. Next on the list are options such as the Pelican M6 and Streamlight TL-2 or TL-3.