[ Thanks to Chris7mas for this link.
“Battle for Wesnoth: Battle for Wesnoth, or BfW for short, is a
popular turn-based strategy game which takes place in a fantasy
universe and has support for singleplayer and multiplayer, official
campaigns (and more available to download), hotseat games. The game
comes by default with 6 factions and takes place over hexagons,
each player deploying his army and trying to kill his opponent.
Wesnoth can be highly modded via WML (Wesnoth Markup Language), and
the add-ons server includes many more maps, factions, eras and
campaigns. Beside for the usual mode which allows up to 9 players
to battle against each other or forming teams, there are also the
rumble maps (very small maps), or the survival ones, or the
multiplayer campaigns or role playing maps. There is also an
unofficial ladder available. Wesnoth is really an awesome, complete
game, with a great community, great online playing, music themes,
map editor, a great helping system, and much, much more.
“AssaultCube: Being based on the Cube engine, AssaultCube is a
very fast-paced first-person shooter with a gameplay that changes
from mode to mode. There are the usual TDM or CTF modes, but also
TOSOK (Team One Shot One Kill), KTF (Keep the Flag), OSOK, LSS
(Last Swiss Standing) or even PF (Pistol Frenzy). It doesn’t have
high system requirements and the online servers are most of the
time filled with players.”