a) Lickitung: Most popular asked about. From what I've worked out, the boy who trades Slowbro for Lickitung has moved tower, replaced by some chef. I can't remember which watch-tower. Just try 'em all. If somneone tries to trade you, and it's not the chef, its him. But, you can also find Wild Lickitung in the Mystery Dungeon, but they are incredily rare. I have only ever seen one on the "platform" where Mewtwo is waiting for you, and then only 1 in 30 encounters or so.

b) Tangela: It turns out that this Pokemon is not a one off, and you can get them in the Safari Zone. The man in the tower previously mentioned does not trade you Tangela for Parasect, it instead works the other way around.

c) Mr. Mime: You trade Clefairy, not Abra.

Traders: Who Wants What

Hopefully in time every tradee will be added here. For now though:

Boy in house near Viridian Forest: Trade him Clefairy, get Mr. Mime.
Boy in tunnel entrance near Cerulean City: Trade him Cubone, get Machoke (becomes Machamp)
Old Man in Cinnabar Laboratory: Trade him Golduck, get Rhydon.
Lady in Cinnabar Laboratory: Trade her Growlithe, get Dewgong.
Lab technician in Cinnabar Laboratory: Trade him Kangashkhan, get Muk.
Chef in Fuschia Watchtower: Trade him Tangela, get Parasect.

GYRADOS

GYRADOS CAN BE CAUGHT IN THE WILD!!!!! Yes! Outside the Warden's house in Fuschia City, at the pond you usually only get Magikarps and Poliwags from, if you use the Super Rod, about 1 in ten fights will be against a G-G-GYRADOS!

Pokemon Locations

A list of Pokemon in order and where you can find them on the map (if you can). INCOMPLETE

Pallet Town: Pikachu (ONE), (fish) Staryu, Tentacool, Magikarp
Route 1: Pidgey, Rattata
Route 2: Pidgey, Rattata, Nidoran F, Nidoran M
Route 22: Rattata, Spearow, Nidoran F, Nidoran M, Mankey, (fish) Poliwag
Viridian City: (Fish) Poliwag
Viridian Forest: Caterpie, Metapod, Pidgey, Pidgeotto
Routes 3,4: Rattata, Spearow, Sandshrew, Mankey
Mt. Moon: Zubat, Paras, Clefairy, Geodude, Sandshrew
Cerulean City: Bulbasaur (ONE)
Route 24: Pidgey, Pidgeotto, Oddish, Venonat, Bellsprout, Charmander (ONE), (Fish) Krabby, Kingler
Route 25: Pidgey, Pidgeotto, Oddish, Venonat, Bellsprout, (Fish) Krabby, Kingler
Routes 5,7: Pidgey, Pidgeotto, Rattata, Jigglypuff, Abra
Route 6: Pidgey, Pidgeotto, Rattata, Jigglypuff, Abra, (surf) Psyduck, Golduck, (Fish) Goldeen
Vermillion City: Squirtle (ONE), (Fish) Tentacool
Route 11: Pidgey, Pidgeotto, Rattata, Drowsee, (Fish) Tentacool
Diglett's Cave: Diglett, Dugtrio
Route 9: Rattata, Raticate, Spearow, Fearow, Nidoran F, Nidorina, Nidoran M,
Nidorino, (Fish) Krabby, Kingler
Route 10: Rattata, Raticate, Nidoran F, Nidoran M, Machop, Magnemite
Rock Tunnel: Zubat, Machop, Geodude, Onix
Route 8: Pidgey, Pidgeotto, Rattata, Jigglypuff, Abra, Kadabra
Celadon City: (Exchange) Vulpix, Abra, Wigglytuff, Pinsir, Scyther, Porygon, (Fish) Goldeen
Saffron City: HitmonChan, Hitmonlee, Lapras.
Pokemon Tower Gastly, Haunter, Cubone
Routes 12: Pidgey, Pidgeotto, Oddish, Gloom, Bellsprout, Weepinbell, Farfetch'd, (surf) Slowpoke, Slowbro, Snorlax(only one), (Fish) Horsea, Seadra
Route 13: Pidgey, Pidgeotto, Oddish, Gloom, Bellsprout, Weepinbell, Farfetch'd, (surf) Slowpoke Slowbro, (fish) Horsea, Seadra
Routes 14,15: Pidgeotto, Oddish, Gloom, Venonat, Venomoth, Bellsprout, Weepinbell
Fuschia City: (Fish) Magikarp, Poliwag, Goldeen, Gyrados.
Safari Zone: Nidoran F, Nidorina, Nidoran M, Nidorino, Paras, Parasect, Exeggcute, Cubone, Marowak, Rhyhorn, Chansey, Tangela, Kangaskhan, Scyther, Pinsir, Tauros, (Fish) Magikarp, Goldeen, Dratini, Dragonair (?????)
Routes 16: Rattata, Raticate, Spearow, Fearow, Doduo, Snorlax(only one), (Fish) Shellder, Goldeen, Poliwag
Route 17: Fearow, Ponyta, Doduo, Dodrio, (Fish) Shellder, Goldeen, Poliwag
Route 18: Rattata, Raticate, Spearow, Fearow, Doduo
Power Plant: Magnemite, Magneton, Grimer, Muk, Voltorb, Electrode (two only), Zapdos (only only)
Route 19,20:(surf) Tentacool, (fish) Staryu, Tentacool, Magikarp.
Seafoam Islands: Articuno(only one), Zubat, Golbat, Slowpoke, Slowbro, Seel, Dewgong, Krabby, Kingler, (surf) Tentacool, (fish) Staryu, Tentacool, Magikarp.
Pokemon Mansion: Rattata, Raticate, Growlithe, Grimer, Muk, Ditto
Route 21: Pidgey, Pidgeotto, Rattata, Raticate, (surf) Tentacool, (fish) Staryu, Tentacool, Magikarp
Route 23: Fearow, Nidorina, Nidorino, Mankey, Primeape, (fish) Poliwag, Poliwhirl
Victory Road: Zubat, Golbat, Machoke, Geodude, Graveller, Onix, Moltres (only one)
Unknown Dungeon: Sandslash, Golbat, Gloom, Venomoth, Weepinbell, Graveller,
Lickitung, Rhyhorn, Rhydon, Chansey, Ditto, Mewtwo (only one), (fish) Goldeen, Seaking