This is a list of some of my favorite top 5 minecraft mods that people may or may not have heard about. Please note these mods are in no way organized by their favoritism.

1) Mo'creatures- This mod adds a variety of new hostile and passive mobs to the game.
www.minecraftforum.net/topic/81771-v181-mo-creatures-v2142-with-scorpions-turtles-and-crocodiles/

2) Humans+- This mod adds a very cool variety of hostile and passive NPC players which can befriend you and sometimes fight for you
www.minecraftforum.net/topic/96903-19pre518-humans-v23-now-open-to-suggestions/

3) Single Player Commands: This mod adds very cool options such as flying,instantmining, and other cool tweaks. Their motto is: "Be anyone, Go anywhere, Do anything.
www.minecraftforum.net/topic/94310-19pre5-181-single-player-commands-v213-new-update/

4)Too Many Items- This mod adds infinite material whilst playing minecraft. Any items from other mods show up automatically in TMI.
www.minecraftforum.net/topic/140684-rc2-toomanyitems-in-game-invedit-nov-13/

5)SDK's Gun Mod- This mod adds modern weapons to a classic game. The sheer damage an awesomeness of it is thrilling.
www.minecraftforum.net/topic/86765-181-sdks-mods-v1-finally-updated/

Also please do not spam me saying "WTF WHY DIDN'T YOU ADD THE SUPER KITTIES MOD" (or something like that. These are my favorite mods. Feel free to add some of your favorite mods in the comments, but don't spam me with it.

Copyright- I am in noway stating that these mods belong to me or have been made by me. I just want to show them to the people that don't know about them. I give all credit to the creators for creating such awesome and unique mods. The image is also not mine. Link to image below
www.google.com/imgres?start=24&num=10&um=1&hl=en&biw=1440&bih=781&tbm=isch&tbnid=8okCzRI5wHwjAM:&imgrefurl=http://daedalus-95.deviantart.com/art/Minecraft-Wallpaper-201515350&docid=E0jrvLan3xuQSM&imgurl=http://fc08.deviantart.net/fs71/i/2011/078/c/1/minecraft_wallpaper_by_daedalus_95-d3bz68m.jpg&w=900&h=506&ei=CizETtL8IOnv0gHYgr2RDw&zoom=1&iact=rc&dur=330&sig=103205021867072591743&sqi=2&page=2&tbnh=98&tbnw=174&ndsp=25&ved=1t:429,r:5,s:24&tx=91&ty=63