I'll throw in some fun to play if nothing else melee kits.
The BF3 soldier with a falcon is pretty entertaining. Stagger things then slap them to death, or act like your dream was to punch things with an omni-blade like in the trailers. Far from the most damaging build, but it'll make you laugh. Works great against cerberus, but platinum gets a bit too boss spammy for it. On a side note, maxing frags and running it as a normal kit is also really fun.
The no flamer vorcha soldier is fun if you enjoy being stupidly aggressive and realize the vorcha sentinel and geth trooper do flamer better. I've found it to be a lot more effective on platinum than many other melee builds (barring known top end ones). It's not easy, but it can work. Remember that a melee focused bloodlust tree has less health regen than a normal build!
In both cases I don't take incapacitate on carnage because melee tracking isn't the best on knocked down targets. That spec should also knock the shield of a guardian back. Both kits could be "optimized" a bit better, but that's how I run them anyways.
Quarksman and bat-glove juggy are also fun if you like quirky builds. Marksman rank 2 is all I recommend since rank 3 duration just locks you out of your de-buffs for longer. Tech vulnerability+tac scan actually does pretty good damage (don't take batarian gauntlet). I can't remember if I've used the melee quarian on platinum or not, but I have used the falcon punching juggy on platinum a few times. A juggy who can't heavy melee rep his shields is a challenge, but falcon punching with a giant robot is worth it! Spam geth turret since it restores some shields.