Ive never delt with Tannite, but I do have a decent chemistry background, and have delt with a number of differnent explosive compounds; homemade and professional . So I would like to tell you Tannite guys that there are 3 very stable and easily obtainable metals, that would add a very cool effect to your targets.
What Im refering to is Aluminum, Magnesium, and Titanium. You can find plenty of websites that will sell the three metals in either particulate (dust), shavings, and/or ingots of different sizes. Shaving are the best, dust is too fine, and ingots you have to cut up yourself.
When shaving of any three of these elements is added to an explosive compound, and the compound is dotonated, you get a shower of sparks and moltent metal burning upwards of 5000 degrees, dependant on the metal used. Trust me, it is very cool to watch, especially at night. Obviously though, there is an inherent fire hazard with this.
I picked up an Mg ingot off of ebay a while back for about 8 bucks, put the saws-all to it and had some really nice shaving and wafers to play with. Very fun stuff, but if you go the Magnesium route do some research. When Mg is ignited it burns EXTREMELY hot, and wont be put out easily. Throwing water on burning Mg will usually get you an explosion, as the Mg burns hot enough to break the Hydrogen and Oxygen bonds and the resulting gaseous O and H create a nice red-ox scenario, and can explode quite violently.
Have fun but be careful!