[Omnirizon]

i am quite enthralled with all the la argatha summons, they are very powerful. the argatha specific level 5 tomb oracle is in many situations a far better summon than things such as the level 7 & 8 elemental royalty and golems. e3 d3 h3 mucho hp and they are 'regenable'. e3 and d3 is a very versatile combo; the h3 is icing on the cake. umbrals are cheep cheep cheep and can be summoned by the equally cheepo basic non-cap mage; so you can summon up a storm of them anywhere.

edit: in discrete response to the OP, I guess i would have to say for the moment tomb oracles are my fave, given their cost, position in the research tree, and ability. they are really a lot of bang for relatively little research and gem buck.