Racial bonuses/penalties for small/large creatures.

[Dust]

We all know the familiar ones; smaller creatures are more evasive, and generally get bonuses to being sneaky. Larger creatures hit harder, and can soak more punishment in battle, but are often clumsier or slower. But other than the biological implications - needing more food to live and so on - are there any other good spur-of-the-moment modifiers (both good and bad) one could slap onto a custom race?

[Conners]

Not being able to fit through doorways...? Not being able to reach the top shelf...?

Remember that Reach is also a factor, with size.

[LibraryOgre]

In Shadowrun, Trolls are close to 3m tall, meaning they pay higher lifestyle costs... Food, clothing, furniture, all have to be upsized when you're 300 kilos.

[Rorrik]

Just like long weapons can be restricted at close quarters, some large creatures could be hindered when swinging long arms in narrow corridors.

A large creature's eyes may be further apart and hinder facial recognition or depth perception. Alternatively, if his eyes are close together he may lack peripheral vision.

A small creature can have stronger materials per weight (ie spider web rope) on the other hand, fine mechanics like catapults may breakdown due to more precise stress needs.

[Necroticplague]

In Shadowrun, Trolls are close to 3m tall, meaning they pay higher lifestyle costs... Food, clothing, furniture, all have to be upsized when you're 300 kilos.

Fortunately for the sake of fitting through doorways, they also stoop over a lot (unfortunately for the fitting through, they're a meter wide).

[jackattack]

A large creature that falls or charges into a solid object is going to take more (actual and relative) damage than a smaller one, because mass translates into momentum. (This is why an ant can fall from a balcony with no apparent injury, but a horse is likely to break bones in the same fall.)

Small creatures can negotiate small holes, burrows, and cracks, both to avoid detection and damage.

Large creatures do more collateral damage to the surrounding environment. (Never put your attack rhinos in a chamber supported by lots of columns.)

Small creatures may elicit more collateral damage to the surrounding environment (or their compatriots) by attackers. (When the fighter tries to kill a ferret with a mace and misses, the mace has to go somewhere -- and how many of us would actually try to sweep the ferret sideways rather than bash it with a downward strike?)

When all else fails, a creature with sufficient size (and brains) can simply sit on a smaller opponent and pin it down.