During gameplay, press ~ to drop the console menu and enter the following cheats:

God Mode: god
Fly Mode: fly
No Clipping: noclip
Invisible to Enemies: notarget
Get Weapons: impulse 101
Spawn Item: give
Map List: maps *
Kill Bots: bot_kill
Restart Map: restart
Change Map: changelevel
Restart Round: sv_restartround 1
Bring down the All Deleted Scenes: cl_levellocks 16382
Enables cheats: sv_cheats 1
Make them just stand there: bot_zombie 1
The bots will only buy pistols: bot_pistols_only
Kick the bots: kick
Bots only buy snipers: bot_sniper_only
Make the bot go to specific places: bot_goto_mark #number
Set the bot's difficulty level: bot_difficulty
Bots only use knives: bot_knives_only 1