My favorite splinter is actually split between the water, and dragon splinters. I find the water splinter pretty good for Bronze and Silver leagues, since magic has few counters, and with some additions from Untamed, and dice, it's become a good melee splinter. On the other hand, the Dragon splinter has some powerhouse cards, and is good for taking on the high mana, and infinite mana matches, teaming up with fire, or water.

Out of both, water tends to be used more often, for me.