Akroan Hoplite a decent two drop that can swing for some hefty damage once i get enough creatures out.
Anax and Cymede a fairly cheap 3/2 with first strike and vigilance for 3 mana is pretty sweet plus they make my other creatures stronger and give them trample with heroic.
Aurelia, the Warleader a 3/4 with flying vigilance and haste isn't great for 6 mana, but she allows me to attack twice with everything everyturn. Plus with Boros Charm or Frontline Medic there's minimal risk of losing creatures.
Boros Reckoner is a must have in any boros deck, great for making opponents wary of attacking lest they lose a creature to reckoner, or take significant damage from it. Also part of an infinite lifegain combo with Hopeful Eidolon and Boros Charm or Frontline Medic.
Legion Loyalist is one of those cards that's just great, battalion to give everything first strike and trample as well as protection from tokens, plus he has haste!
Purphoros, God of the Forge is a finisher, dealing 2 damage to my opponent everytime I play a creature, especially since I have a fair number of decently cheap creatures, but most importantly it combines with Assemble the Legion for huge damage.
Tajic, Blade of the Legion i love Tajic, his battalion makes him enormous, and even without it a 2/2 indestructible is still a great blocker. Additionally he's pretty tough to remove.
Dauntless Onslaught is mostly to activate heroic also a decent temporary bonus for two creatures.
Gods Willing can either save a creature or let me get an attack through when i really need it. Also activates heroic, and lets me scry.
Assemble the Legion gives me a ton of wonderful tokens to do with as i please, also when combined with purphorose, god of the forge it can do some mad damage
Spear of Heliod makes my smaller creatures a bit more threatening and has the potential to act as removal if necessary.