Call of Duty!
There are none that are free and similar to runescape, other than a runescape private server.
Yes there is Bin Weevils, Free Realms, Territory War Online etc... .
There are games similar to Roblox, but none of them are free. You may want to try Runescape or World of Warcraft.
yes
You can play halo games online at addictinggames.com, where they have a wide variety of free games, and many of them are similar to halo. I think you would enjoy playing on that website.
Jagex is the developer of Runescape, which has been for several years one of the most popular free to play online games. EA offers a free beta for FIFA online, which is similar to its very popular FIFA series.
Facebook.com has a lot of games such as Words with Friends which is similar to Scrabble. Also, free crossword puzzles can be found on a number of sites such as nytimes.com or boston.com. Both are available to do online or print.
There are a few places with some great games such as Lord of the Rings Online which is a MMORPG similar to World of Warcraft. Also Dungeons and Dragons Online does not require monthly fees.
Driving games are very popular and can be played online for free. One can play them at Truck Games Parking, Free Driving Games, Mouse Breaker, or Free Online Games.
The game Invasion 3 can be played online for free at Addicting Games, Free Online Games, Games List, Played Online, Much Games, Armor Games and QiQi Games.
Castle Defender and other similar games can be played online from many different online game websites. Some examples of these websites include Addicting Games and Kongregate.