Someone mentioned on Reddit how underwhelming as a rare this seemed to be, but as a top-down, guy on a horse with a lance design, I'm unsure as to how to make it "less underwhelming", it harkens back to other multi-french vanillia bombs like Baneslayer, though obviously it is a regular rare, not a mythic.

also - flavor text

I think the best solution is simply to make this uncommon.

Need it to be a rare.

How about a knight lord then? All knights gain +1/+1 and trample, or something else like that would justify the rarity.

This is a good solid card. I want four of it. So it shouldn't be rare.

That doesn't make sense, lol.

But Lord it is!

Small white guy with trample? That's not something that happens in the modern color pie.

Aye, but it does fit flavorfully well. A knight on horseback.

The flavour argument isn't very strong here. You can justify all sorts of colour pie breakages with flavour, but the colour pie needs to keep a mechanical component too. I think trample should change to something else.

I agree that white isn't normally the color of trample, but based on Modern legal cards - Mirror-Sigil Sergeant, is a rhino solider. There is also Bringer of the White Dawn.

And then a bunch of white/green stuff that doesn't count. But it is OK for cards to break out of the color pie on occasion to justify good flavor.

Agreed, to justify good flavor. I don't know if this is good flavor, though. This guy pretty much tells your knights that they can now trample. Why? Is he more reckless than most knights? That would make this guy red... which would end up fitting the color pie again.

You could sell me, if the flavor text dripped with the answer. But, to be honest, I'm having a hard time justifying it in my head. Maybe this guy respects the mission above all esle, and the mission is ignoring the riff raff on the battlefield to tag the Baron, or something of that nature? I could buy that. I think I'd personally just construct a different mechanic based around that idea, though...

To associate this from purely flavor - Knights are often on horseback, well armored and armed(+1/+1) and ride over(trample) the enemy before them, they often use longer weapons(first strike). I think a good piece of artwork could sell this card as what I'm intending it to be - but an hour of searching google has landed not much, but take this guy:

http://s.cghub.com/files/Image/403001-404000/403134/597_max.jpg

and give him a lance/spear and this background: http://digital-art-gallery.com/oid/115/640x412_19868_Battle_2d_fantasy_medieval_knight_rider_picture_image_digital_art.jpg

But Magic the Gathering horses rarely trample over dudes. Trampling horses might seem like a reasonable choice in Dungeons and Dragons, say, but in Magic, they aren't big enough. Trampling creatures in Magic are normally triple the size of a normal human.

I'm not saying this guy can't trample... I'm just asking why can this guy when others can't? And why does he inspire other horses to do what they aren't naturally inclined to do?

The artwork could do it; make the large pointed object be a bridge flung by capapult. But that kind of visual humour also makes the card red :)

Hmmm,

Catapul-Arm Giant - 5RR
Creature - Giant
Reach
Sacrifice a land or artifact with converted mana cost 4 or greater, T: ~ deals damage equal to its power to each creature target player controls.
6/5

But lands don't have a converted mana cost, so you could (almost) never sacrifice them to pay for that ability.
Alex's point about flavor wasn't that the flavor of this having or granting trample isn't strong. It's that designing from flavor and then justifying an out-of-color design by flavor is a mistake-ridden path. Just look at Hornet Sting and read about how Maro feels about that card to know what we're talking about.

Its land, or artifact with converted mana cost 4 or greater. Not Land with converted mana cost 4 or greater or an artifact with ...but irrelevant discussion to the card itself.

I'll take some suggestions on how to modify the card to see it fit its flavor better - needs to stay a Lord for sure.