I typically try to keep my distance when I fight other Assassins or confront Warriors, whittling down their HP so I can keep my own topped off. Rain of Vengeance is typically the Ult I pick in most of my matches so that I can secure kills for myself and my team.

Blood for Blood and Giant Killer are my two favorite talents for when I have to deal with some really beefy enemies, as their damage increases according to the max HP of the target. In other words, the more HP you have, the more these two talents will hurt. Giant Killer also synergizes very well with Vigorous Assault, allowing me to "out-tank" enemies with large amounts of HP, but inferior DPS.

As for the Caltrops - it's hilarious how easy they are to avoid (because no one ever walks around them).

Caster - This build a bit similar to the "DIE, DIE, DIE!" build, but designed to provide a more well-rounded touch. Blood for Blood will be very useful in dangerous situations, but never use Strafe if you're low on HP; you never know when a Zeratul or Nova is gonna insta-kill you.

Sustain - This build is all about staying alive and keeping your distance. With this build, Valla can sometimes go toe-to-toe with foes that can kill her almost instantly, such as Zeratul and Nova. Keyword: SOMETIMES

VENGEANCE RAINS FROM ABOVE! - Obviously, this is a joke build centered around Rain of Vengeance. The build has a surprising amount of potential, but your biggest worry will be your mana. Valla's spells are spammable, but they're also huge mana sinks.

Fight me or I'll shaft you! OuO - This is essentially a hilariously powerful "right click" build. You should try to get Rain of Vengeance if you plan on going for this build, as it may prove difficult to get their attention if you try to Strafe them to death. I mean, who CAN'T notice those big-*** stuns?

DIE, DIE, DIE! - Death Blossom = Strafe. Need we say more? :P