Templar has some flashy skills - and I enjoy the attacking morphs for stamina Templar.
Binding Javelin is one of my favorite skills in the game. You conjure a light-infused spear and throw it at an enemy to knock them clean off their feet and send them flying backwards.
Power of the Light calls down a beam of light that locks onto your enemy and duplicates and stores some of the damage that you're doing. Then it explodes on the enemy after 6 seconds.
Biting Jabs will give you a large light-infused spear that jabs away at multiple enemies in front of you.
DK is either fiery or bright poison green.
Templar is flashy white/gold.
MagSorc is lightning bolts.
Wardens have bright green/teal blue ice storms and creature summons.
If you want flashy, I would say sorc, dragonknight, or warden.
Sorcerors can lay down lightning like crazy, and overload gives you papa palpatine mode. A sorc tank with thunderbug and livewire would be pretty fun too.
Dragonknights can put out a lot of fire effects, I run a dk mag tank with elf bane and seducer and can spam fire aoe's all day.
Warden has a lot of cool ability animations and visual flare, particularly with nature's balance abilities.