In-Game Trades

A staple of the Pokemon series is the ability to trade Pokemon, and as in every previous version you're given a few opportunities to do this in-game. Unlike previous generations though there are no exclusive Pokemont to be found in these in-game trades, making them somewhat redundant. As in Gold and Silver they sometimes can aid you with parts of the game where you may have a massive type disadvantage against a particular Gym Leader and little options in the wild. What's unique about these monsters is that they each have a highly boosted contest stat, a few points in the other contest stats, and sheens all set to 10. These games sport the fewest trades at just three:

#296 Maukhita

Location: Rustboro City
Contest Stat: Tough

The first in game trade you'll probably encounter is this one in the house beside Rustboro Gym. Here you can trade the relatively rare Slakoth for a Pokemon you cannot obtain at this point, Makuhita. This can be useful for the gym if you picked Torchic and do not wish to grind it up to Level 16. Makuhita also comes equipped with X Attack to boost your chances at victory.

Level ??
Hold Item:

X Attack
Hardy Nature.
Date Received. Pokémon Trade. Received at Level ??
Trader requests a Slakoth
#300 Skitty

Location: Fortree City
Contest Stat: Cute

This trade is in the treehouse by the Fortree Pokémon Center. Although it seems a bit pointless to trade the hard-to-obtain Pikachu for a Skitty (especially considering Pikachu would be a lot more helpful in this and coming Gym battles), it is one of the few ways in this generation to obtain Glitter Mail, which Skitty holds.

Level ??
Hold Item:

Glitter Mail
Timid Nature.
Date Received. Pokémon Trade. Received at Level ??
Trader requests a Pikachu
#222 Corsola

Location: Pacifidlog Town
Contest Stat: Beauty

Now this is a bad trade. Located in the house below the Pokemon Center, you are asked to trade Bellossom, which takes some effort and a rare stone to obtain, for the common Corsola which you can just fish for on Route 128. Should you accept this offer (you shouldn't), you can obtain the otherwise difficult to find Tropic Mail.

Level ??
Hold Item:

Tropic Mail
Calm Nature.
Date Received. Pokémon Trade. Received at Level ??
Trader requests a Bellossom