The Fenix TK15 has been a best seller since it was released late last year. The light has two switches, a traditional one on the rear of the light that gives you momentary and constant on, plus one up by the head that will switch modes. The secondary light is the only way to switch modes or activate the flashing modes, so the rear switch can give you 100% reliable activation if you want to stick to one mode or at least always get back to the mode you last used.
The TD15 is one of the higher output lights that are currently available in that size, so it has plenty of lumens for finding your dog when he refuses to come in at night super tactical stuff.