I've recently been using a bunch of mods all together: Metallurgy 4, Chisel, Balkon's Weapon mod, Not Enough Items, Bibliocraft, Damage Indicators, Disaster Craft, Dungeon Pack, Sync (clone mod), Block Launcher, and Zyn's HUD. All of these work together. The dungeon Pack works quite well with Disaster craft, as it adds dungeons and stuff to loot. Metallurgy is great. You mine ores, some of which you can make into tools and armor, some of which you have to grind into dust and then alloy. Some swords have a chance to inflict an effect on an enemy (fire aspect, poison, blindness, etc). There are also some really good ores you can get in the Nether. Chisel allows you to chisel blocks, and make really nice looking houses.
This is quite a fun mod, there are a few bugs, but it is still playable. WARNING! Only play this mod on one world, otherwise you have to start over on the other world.
Also, you sometimes meet (I think only if you are on easy, possibly instead of mobs) NPC trainers, who you can fight. You press 'R' to send out your Pokémon, and if you have more than one, use [ and ] to scroll through the list. If you hit another Pokémon with yours when you send it out you start a fight. Sometimes Pokémon start a fight with you.
This mod adds a new block, compressed raw porkchop. You place this down, and then right-click it with a Nether Star to summon a giant pig from the sky. This pig is enormous, don't summon it near anything it might walk into/stand on. Pigzilla is very destructive.
The giant pig uses the pig texture from whatever texture pack you have, just enlarged.
This mod adds... Helicopters & Airplanes, as well as some turrets you can place & operate. There are many, many different vehicles. Most aircraft have multiple seats, so you can carry more than one person in it.
All of the aircraft & the turrets. The pit in front of the huge turret is what the shells from it do.
This is probably my favorite mod. Ever. The entire world is set out according to J.R.R. Tolkein's map of Middle earth, and depending on what you do (and mostly who you kill) different people either like you or hate you. You always start in the Shire, and then you go wherever you like. There is a map, and you can teleport to the capital of any *biome* that you've visited.
There are lots of races, Ents, Hobbits, People from Harad, etc. Pretty much every race there is in Middle-Earth.