I' got the places for all the - Resident Evil 4
I' got the places for all the weapons
Punisher-complete the blue medallion quest
Blactail-available from the merchant after getting into castle (i think)
Broken Butterfly- 1st castle merchant
Killer 7 - near the end of the game available from merchants on the island
NOTE:Killer 7 may be more powerful than Broken Butterfly at first but only has 3 more upgrades after that but the Broken Butterfly after all the firepower upgrades is a 50.0 which can take down a boss in 4 hits.
Handcannon-available after beatin the game
Matilda- after beating the game available at 1st merchant
Infinite rocket launcher- after beating game but cost 1,000,000 ptas
Chicago typwriter (infinite ammo) ( machine gun)-after beating assignment ada also 1,000,000 ptas
Sniper bolt action-1st merchant
Tmp- 1st merchant
Rapid fire sniper-1st castle merchant
Striker- merchant before salazar's fight
Riot gun-1st merchant in castle
The guns I recommend having are the: fully upgraded TMP in ammo and firepower,
Rapid fire sniper, striker, fully upgraded blacktail in firepower, and broken butterfly.
These are the guns I have and have gotten me through the game nearly 2 times
Also if you can afford it the chicago typewriter the reason I say this is because if you get the rocket launcher leon can also suffer if the enemis get too close.