Since Jackard was looking for this sort of thread as he mentioned in another I was just reading I thought I'd give it a go. Talk about what other games you play or played before you came to H&H.
Games I currently play:
Battle for Wesnoth - Turn based, fantasy themed, Open source Strategy with sinlge player campaigns and multiplayer scenarios and PvP. Hundreds of user made addons and it's own markup language for user made content.
Wolfenstein: Enemy Territory - Haven't played this as much, i'm still something of a noob. It's a WWII themed FPS with elements of strategy and character development. Wins are based on offensive and defensive objectives rather than kills.
Alien Arena - I'm a pro here. Long ago ID software released the Quake 2 source code and several mods have been made from it. ALien arena is the longest surviving and arguably the most popular. It has a growing player base with every update. THe engine has been cleaned up quite a bit and significant graphical improvements made. Anti-lag is in it's finest evolution since the 7.33 release. You can almost always find a game for CTF and two or three weekly tourneys are held most often for instagib.
Warzone 2100 - Just downloaded this Open Source RTS strategy game. I'll edit later with my opinions.
Games I used to play:
Runescape - My first MMO. If nothing else it taught me a lot about what I don't want out of an online game. =)
ShadowBane - Until its demise at the release of Age of Conan and Darkfall. Many of those that made the disappointing exodus have returned to the SBEmu project to ressurect Shadowbane by emulating the server code and. ETA for live is overdue but speculation is for something this summer. Recent updates have given promise of a much sooner release. Shadowbane is a PK-almost-anywhere with only a handful of safezones on a fixed map. Gold is gathered and XP is gained by WoW style farming but character development is very rapid (a couple of days of dedicated grinding can produce a max level char). Gold is used to purchase buildings, walls and upgrades for player guild established cities. Mines are fought over for mineral resources that are used to produce high end weapons and armor. The game is highly PvP but mostly GvG (Guild versus Guild) with major GvG events being held to siege or defend cities or mines at prearranged times. Players can create a huge variety of characters from several races, classes and professions with a high level of customization of stats and skills to make character building a highly debated issue over optimal design choices. Servers can be made ARAC (All Races All Classes) and Lore (Guilds must choose a faction which limits race selection and race selection limits available professions). The Emulated server will likely be ARAC until (if ever) a large enough player base is formed to support a lore server.
And yes everything I've mentioned here is free to play. Although I did pay for an RS subscription for several months.