Any Pokemon in the Field egg-group can breed with samurott, besides Ditto, thats it.
Listed out in aphabetical order that looks like this:
Absol
Aipom
Ambipom
Ampharos
Arbok
Arcanine
Beartic
Bibarel
Bidoof
Blaziken
Blitzle
Bouffalant
Buizel
Buneary
Camerupt
Chimchar
Cinccino
Combusken
Cubchoo
Cyndaquil
Darmanitan
Darumaka
Deerling
Delcatty
Delibird
Dewgong
Dewott
Diglett
Donphan
Drilbur
Dugtrio
Dunsparce
Eevee
Ekans
Electrike
Emboar
Emolga
Empoleon
Espeon
Excadrill
Exploud
Farfetch'd
Flaaffy
Flareon
Floatzel
Furret
Girafarig
Glaceon
Glameow
Golduck
Granbull
Growlithe
Grumpig
Heatmor
Herdier
Hippopotas
Hippowdon
Houndoom
Houndour
Infernape
Jolteon
Kecleon
Krokorok
Krookodile
Leafeon
Liepard
Lillipup
Linoone
Lopunny
Loudred
Lucario
Luxio
Luxray
Mamoswine
Manectric
Mankey
Mareep
Mawile
Meowth
Mienfoo
Mienshao
Mightyena
Miltank
Minccino
Monferno
Munna
Musharna
Nidoking
Nidoran♀
Nidoran♂
Nidorino
Ninetales
Numel
Nuzleaf
Oshawott
Pachirisu
Panpour
Pansage
Pansear
Patrat
Persian
Phanpy
Pignite
Pikachu
Piloswine
Piplup
Ponyta
Poochyena
Primeape
Prinplup
Psyduck
Purrloin
Purugly
Quagsire
Quilava
Raichu
Rapidash
Raticate
Rattata
Rhydon
Rhyhorn
Rhyperior
Samurott
Sandile
Sandshrew
Sandslash
Sawsbuck
Scrafty
Scraggy
Sealeo
Seedot
Seel
Sentret
Serperior
Servine
Seviper
Shiftry
Shinx
Simipour
Simisage
Simisear
Skitty
Skuntank
Slaking
Slakoth
Smeargle
Sneasel
Snivy
Snubbull
Spheal
Spinda
Spoink
Stantler
Stoutland
Stunky
Swinub
Swoobat
Tauros
Teddiursa
Tepig
Torchic
Torkoal
Typhlosion
Umbreon
Ursaring
Vaporeon
Vigoroth
Vulpix
Wailmer
Wailord
Walrein
Watchog
Weavile
Whismur
Woobat
Wooper
Zangoose
Zebstrika
Zigzagoon
Zoroark
Zorua
And just for Kyron: Ditto
