I'm not trying to yuck your yum but personally I wouldn't even consider carrying one on my kit for any kind of defensive use. For one thing it's a couple extra pounds that I would rarely use and for another I wouldn't want to put up with the endless ribbing from my buddies. The idea of a "tactical tomahawk", to be used for any kind of fighting, is pretty mall ninja/tacticool geek in my eyes. I don't do a lot of breaching but the guys that do prefer actual purpose built breaching tools. A manual breach is no joke and it's not the time to be ****ing around with toys. Furthermore I don't see a huge advantage a hawk would have over better weapons that weight the same, like a pistol, and I don't see how it could be easily carried or deployed faster than a fixed blade knife. I also don't see it being as useful as a knife for every day tasks and emergency uses like cutting straps, clothing etc.
However I often carry a small hatchet in my ruck when I'm in the woods. It's just for camp chores. I'm using a Gransfors Bruks Wildlife Hatchet these days mainly because it's light and because I like it. It made my Swamp Rat chopper obsolete and I can use the back to hammer in tent stakes and stuff. The Fiskars hatchet also looks like a great buy and won't break the bank. Wetterlings is also supposed to make a great hatchet but I've not used one. I like my GB enough that I'm considering picking up one of those fancy custom hatchets you see on bladeforums.com
I've never seen a real life meateater that carried a tomahawk on his kit. The closest was one guy that used to carry something akin to the
Lee Valley Box Tool for conducting searches.