Recs.
Updated
Open source 3d fast paced first person shooter. Simple and easy to use. Cross platform.
SpecsUpdate
Pros
Pro Interesting weapon design (for an arena shooter)
All arena shooters basically use Quake or UT weapon system. However, Xonotic has an interesting variety of weapons (larger selection than most) with elements from both UT and Quake but added some of their innovative ideas. Some of the weapons have a bit of overlap and feel a bit forced, but other weapons really make the game stand out.
Pro Impressive graphics, especially for an open source game
Open Source games are not always known for their high-quality graphics. This can often be caused by the games being designed by committee in that many different people may work on the graphics, even in the same areas, which can cause plenty of inconsistencies. Luckily, Xonotic does not suffer from this problem as the whole of the game has consistent looks that are actually quite impressive.
Pro Quake inspired gameplay
Xonotic has drawn inspiration from the mechanics of Quake, which is based on quick movement and rapid fire. It is more active than many other FPS games, which involve stealth and camping, because it features a more open world with many different types of guns available to collect.