MileHiCon  is an annual science fiction/fantasy convention held in Denver, Colorado in October. It is primarily literary, although it also has an art show, dealers' room, the Critter Crunch (similar to Robot Wars), the Critter Float-illa (robotic competition in the hotel pool), a video room, anime room, masquerade, gaming, bat'leth tournament, and programming on science, writing, literary, media and fannish topics. It runs its own track of kid-friendly, interactive programming and also hosts the Avistrum Academy of Sorcery. It is run by MileHiCon, Inc., a Colorado not-for-profit corporation, and donates money each year to local literacy programs. 

http://www.milehicon.org/

HexaCon is a Denver-based convention for:
Board games
Role-playing games (RPGs)
Miniatures games
and Train games

https://www.hexacondenver.org/