Minegunner

AKA Ye olde minegunner

Well, if you do want some shooting action, but still want to stay within the bounds of generic Minecraft theme, this is a mod for you!

It adds four different flintlock-style pistols into the game - they are very deadly, yet cumbersome and require quite a lot of preparations to actually use them to any good extent.

Also, I do recommend that you use some other mods which add more monsters and/or challenges into the game, namely Mo' Creatures, Nightmare mod, and the like. Vanilla monsters are easy enough as they are, you don't need guns to bring them down!

From left to right:

1) A "stone-made" jury-rigged one-shot pistol. Shoots pebbles, which means that you don't have to create actual bullets. Low damage, though -- and it also have quite a good chance of exploding right in your hand! That's what you get for using cheap kind of materials.

(There's also a little "easter egg" thing available with it. Feel free to either find it in game, or decompile the code.)

2) An iron flintlock pistol. The proper variant this time - this one does a lot of damage, and is capable of killing every vanilla and most add-on monsters in a single shot. A single shot is all that it does, though - you have to reload it each time. Or keep several of them ready in your quickbar.

3) An exquisite diamond-encrusted six-barreled pepperbox. Obviously enough, it is able to shoot the whole six times before reloading. It's more ammo-hungry if you do reload it in the field, though. Also deals less damage with each bullet, compared to #2. Also a bit less accurate. But hey, you will get six shots!

4) Ye olde "shotgun" a.k.a. blunderbuss pistol! A gunpowder-hungry beast, this thing is capable of dealing quite a lot of damage at the point blank range. Not so much on any significant distance, though. But, now you have some options with it!

Load it with gravel for a "normal" weak-ish shot, or try some more exquisite materials: netherstone will give you a weak, but flaming shot, capable of setting creatures and things on fire! Or just use some obsidian to get a significant boost in raw damage - with some lucky shot, you may even be able to dispatch several enemies at once.

Remember, though: blunderbuss is a single-shot only. Bring some spare ones with you!

Of course #2 and #3 also require bullets, and all guns require gunpowder! There are also recipes to make that as well.

Also, you should keep your gun in a really nice and clean state, if you want good results with it. Each and every gun (except the jury-rigged stone gun, which isn't repairable) can be repaired with some clever application of some iron pieces and a little bit of cloth. Don't use guns in a bad condition, you have been warned!