Eradica first, reasons have been said.. but to my mind it looks like the most detail was put into it. However the back is not so interesting.. take a look.. the engines are too small and it just looks unfinished from behind. But nevermind.
That same point can be said for the VL titan.. underneath is just grey...
Coronata second, i love this titan for the effects of the ring at the top..
Ragnarov lastly due to its awesome gun totting self. Nothing inspirational there, but on the other hand it's a certain show of power. I like it.
Caps... easy, Radiance, because it looks like a battleship. Progneitor... cus it just looks nice. For some reason i really like the Halcyon also.. Advent caps just look nice.