If it should be a mod for public servers, I’d suggest:
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!maplist + !vote
Something like in Jaymod’s EnhancedMod - shows all maps you can !vote, time when last played, how many votes were called on it:

- I would add how many times was it played on current day
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!freeze [name or number] / !unfreeze [name or number]
Player gets frozen till !unfreeze and can’t use /reconnect
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!objective [on/off]
Prevents players from planting dynamites, capturing flags, stealing objective etc. (with disabling entities, not classes and weapons)
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!switch [name1 or number] [name2 or number]
Switches two players teams.
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!rules [name or number or -all]
Shows server rules (in some rules.cfg file) in console.
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!class [soldier, medic, engineer etc.] [-all]
Allows to choose only one class.
The rest - all useful Jaymod/other mods commands with shortcut support like !li, !h !finger !banuser !banli !ban !userli !baninfo !kick !mute !seen !set !put !pause !next !restart !splat !rename etc.
Some funny one-weapon wars like !dynamitewar !pistolwar !sniperwar !panzerwar !knifewar !riflewar !grenadewar etc.
And of course some other funny commands like !throw !launch !headshotwar !speed !gravity !pants etc.