Battle Moveset

A Good Moveset for Swellow would have to be this:

Attacks:

Facade
Steel Wing
Hidden Power Ground
Aerial Ace

Items Attached:

Choice Band

Preferred Nature:

Adamant

Strategy Using Swellow

This moveset requires a little bit prediction and hopefully, some stupidity on the behalf of your opponent. Hopefully, they'll try and do some status damage, poisoning might be your best chance.
Anyways, if they do manage to poison you, this triggers two things, firstly: Swellow's guts ability, which raises its attack for every turn its poisoned/paralyzed etc. The 2nd thing is does is double Facade's attack strength.
So this will result in STAB + Double facade power + extra strength from Guts + Choice band increase, which should result in a quite powerful attack. Although it may take time to set up and require alot of prediction. With Swellow's speed, it should strike first most of the time.
Swellow is a much better pokemon than Pidgeot, with better speed and the guts ability, of course its better. Anyways, the other three moves are required if you don't want to use Facade against your opponent.
Swellow doesn't learn many other moves, so Steel wing and HP ground have to be used, or replace HP Ground with a different Physical HP. Overall, Swellow has the potential to do serious damage to your opponent's team, if you manage to get all the factors right.

EV Corner:

Max out the EVs in Attack & Speed for Swellow with any remaining in Defense

Strategy Against Swellow

Swellow's Defenses are both below average, however it's Special Defense is lower than it's Physical. So attack with a volley of Special Attacks or Ice, Electric or Rock Type Attacks and it'll be down in no time

Contest Moveset

A good Contest Moveset for Swellow would have to be this for the Cool Contest best with Lonely, Adament, Naughty or Brave Nature:

Attacks:

Aerial Ace
Double Team
Double Edge
Hyper Beam

Items Attached:

Red Scarf

Strategy Using Swellow

If you do the attacks in this following order you should have very few problems; 1st - Aerial ace, 2nd - Double team, 3rd - Double edge, 4th - Aerial ace, 5th - Hyperbeam

Locations in Games

Ruby/Sapphire Route 115 Colosseum Trade from R/S Fire Red/Leaf Green Trade from R/S

Animé Appearences

Swellow has had a few Appearences. First, Vito Winstrate had one and secretly used it to protect his family, after that a trainer used it in the PokéRinger match...and in that match, Ash's Taillow also evolved into a Swellow and was used thus. After that, Winona had a Shiny Swellow and used it in battle against Ash's Grovyle and Swellow Episode 322: Winstrate Family! 4 Vs 4! Episode 356: Beginning Challenge! Sky Match - PokéRinger! Episode 357: The Mansion of Shuppet! Episode 358: Forest's Fighting King! Breloom VS Combusken! Episode 360: Fortree City's Feather Carnival! Episode 361: Fortree Gym! Battle In The Sky! Movie 7: Visitor Of The Space Fissure! Episode 366: Arrival in Lilycove City! Pokéblocks and Aerial Ace!