Sorry for posting it in a dead theme, but I think it will be useful for someone - a fresh list of hidden cvars.
Code:
Locked ConVar: sv_showanimstate
Locked ConVar: sv_showanimstate_log
Locked ConVar: mp_feetyawrate
Locked ConVar: mp_facefronttime
Locked ConVar: mp_ik
Locked ConVar: sv_netvisdist
Locked ConVar: sv_suppress_viewpunch
Locked ConVar: sv_force_transmit_ents
Locked ConVar: sv_optimizedmovement
Locked ConVar: sv_stopspeed
Locked ConVar: sv_maxspeed
Locked ConVar: sv_accelerate
Locked ConVar: sv_airaccelerate
Locked ConVar: sv_wateraccelerate
Locked ConVar: sv_waterfriction
Locked ConVar: sv_footsteps
Locked ConVar: sv_rollspeed
Locked ConVar: sv_rollangle
Locked ConVar: sv_friction
Locked ConVar: sv_bounce
Locked ConVar: sv_maxvelocity
Locked ConVar: sv_stepsize
Locked ConVar: sv_backspeed
Locked ConVar: sv_waterdist
Locked ConVar: sv_pushaway_force
Locked ConVar: sv_pushaway_min_player_speed
Locked ConVar: sv_pushaway_max_force
Locked ConVar: sv_pushaway_clientside
Locked ConVar: sv_pushaway_player_force
Locked ConVar: sv_pushaway_max_player_force
Locked ConVar: sv_unlag
Locked ConVar: sv_maxunlag
Locked ConVar: sv_lagflushbonecache
Locked ConVar: sv_unlag_fixstuck
Locked ConVar: sv_unlag_debug
Locked ConVar: sv_pushaway_clientside_size
Locked ConVar: mp_capstyle
Locked ConVar: mp_blockstyle
Locked ConVar: mp_capdeteriorate_time
Locked ConVar: mp_showroundtransitions
Locked ConVar: mp_showcleanedupents
Locked ConVar: tf_demandloaditems
Locked ConVar: item_quality_chance_unique
Locked ConVar: item_quality_chance_rare
Locked ConVar: item_quality_chance_common
Locked ConVar: tf_obj_build_rotation_speed
Locked ConVar: tf_obj_max_attach_dist
Locked ConVar: sv_ignore_hitboxes
Locked ConVar: anim_showstate
Locked ConVar: anim_showstatelog
Locked ConVar: mp_showgestureslots
Locked ConVar: mp_slammoveyaw
Locked ConVar: steamworks_show_uploads
Locked ConVar: tf_maxspeed
Locked ConVar: tf_showspeed
Locked ConVar: tf_avoidteammates
Locked ConVar: tf_solidobjects
Locked ConVar: tf_clamp_back_speed
Locked ConVar: tf_clamp_back_speed_min
Locked ConVar: tf_scout_air_dash_count
Locked ConVar: tf_force_holidays_off
Locked ConVar: tf_caplinear
Locked ConVar: tf_stalematechangeclasstime
Locked ConVar: tf_arena_force_class
Locked ConVar: tf_arena_change_limit
Locked ConVar: mp_waitingforplayers_time
Locked ConVar: tf_gamemode_arena
Locked ConVar: tf_gamemode_cp
Locked ConVar: tf_gamemode_ctf
Locked ConVar: tf_gamemode_payload
Locked ConVar: tf_bot_count
Locked ConVar: tf_obj_gib_velocity_min
Locked ConVar: tf_obj_gib_velocity_max
Locked ConVar: tf_obj_gib_maxspeed
Locked ConVar: tf_obj_upgrade_per_hit
Locked ConVar: object_verbose
Locked ConVar: obj_damage_factor
Locked ConVar: obj_child_damage_factor
Locked ConVar: tf_fastbuild
Locked ConVar: tf_obj_ground_clearance
Locked ConVar: tf_obj_damage_tank_achievement_amount
Locked ConVar: tf_sentrygun_damage
Locked ConVar: tf_sentrygun_mini_damage
Locked ConVar: tf_sentrygun_ammocheat
Locked ConVar: tf_sentrygun_newtarget_dist
Locked ConVar: tf_sentrygun_metal_per_shell
Locked ConVar: tf_sentrygun_metal_per_rocket
Locked ConVar: tf_sentrygun_notarget
Locked ConVar: tf_sentrygun_max_absorbed_damage_while_controlled_for_achieveme
Locked ConVar: tf_sentrygun_kill_after_redeploy_time_achievement
Locked ConVar: tf_teleporter_fov_start
Locked ConVar: tf_teleporter_fov_time
Locked ConVar: tf_playerstatetransitions
Locked ConVar: tf_weapon_ragdoll_velocity_min
Locked ConVar: tf_weapon_ragdoll_velocity_max
Locked ConVar: tf_weapon_ragdoll_maxspeed
Locked ConVar: tf_damageforcescale_other
Locked ConVar: tf_damageforcescale_self_soldier_rj
Locked ConVar: tf_damageforcescale_self_soldier_badrj
Locked ConVar: tf_damagescale_self_soldier
Locked ConVar: tf_damage_lineardist
Locked ConVar: tf_damage_range
Locked ConVar: tf_feign_death_damage_scale
Locked ConVar: tf_max_voice_speak_delay
Locked ConVar: tf_spy_invis_time
Locked ConVar: tf_spy_invis_unstealth_time
Locked ConVar: tf_spy_max_cloaked_speed
Locked ConVar: tf_max_health_boost
Locked ConVar: tf_invuln_time
Locked ConVar: tf_player_movement_stun_time
Locked ConVar: tf_soldier_buff_pulses
Locked ConVar: tf_boost_drain_time
Locked ConVar: tf_damage_events_track_for
Locked ConVar: tf_useparticletracers
Locked ConVar: tf_spy_cloak_consume_rate
Locked ConVar: tf_spy_cloak_regen_rate
Locked ConVar: tf_spy_cloak_no_attack_time
Locked ConVar: tf_scout_energydrink_regen_rate
Locked ConVar: tf_scout_energydrink_consume_rate
Locked ConVar: tf_scout_energydrink_activation
Locked ConVar: tf_feign_death_duration
Locked ConVar: tf_cheapobjects
Locked ConVar: tf_scout_stunball_base_duration
Locked ConVar: tf_scout_stunball_base_speed
Locked ConVar: sv_proj_stunball_damage
Locked ConVar: tf_scout_stunball_ball_regen_rate
Locked ConVar: tf_scout_bat_launch_delay
Locked ConVar: tf_flamethrower_velocity
Locked ConVar: tf_flamethrower_drag
Locked ConVar: tf_flamethrower_float
Locked ConVar: tf_flamethrower_flametime
Locked ConVar: tf_flamethrower_vecrand
Locked ConVar: tf_flamethrower_maxdamagedist
Locked ConVar: tf_flamethrower_shortrangedamagemultiplier
Locked ConVar: tf_flamethrower_velocityfadestart
Locked ConVar: tf_flamethrower_velocityfadeend
Locked ConVar: tf_flamethrower_burst_zvelocity
Locked ConVar: tf_flamethrower_burstammo
Locked ConVar: tf_grenadelauncher_chargescale
Locked ConVar: tf_grenadelauncher_livetime
Locked ConVar: tf_grenadelauncher_min_contact_speed
Locked ConVar: tf_grenade_forcefrom_bullet
Locked ConVar: tf_grenade_forcefrom_buckshot
Locked ConVar: tf_grenade_forcefrom_blast
Locked ConVar: tf_grenade_force_sleeptime
Locked ConVar: tf_pipebomb_force_to_move
Locked ConVar: tf_pipebomb_deflect_reset_time
Locked ConVar: tf_sniper_jar_regen_rate
Locked ConVar: weapon_medigun_damage_modifier
Locked ConVar: weapon_medigun_construction_rate
Locked ConVar: weapon_medigun_charge_rate
Locked ConVar: weapon_medigun_chargerelease_rate
Locked ConVar: tf_medigun_lagcomp
Locked ConVar: mp_forceactivityset
Locked ConVar: tf_grenade_show_radius
Locked ConVar: tf_grenade_show_radius_time
Locked ConVar: tf_meleeattackforcescale
Locked ConVar: tf_rocket_show_radius
Locked ConVar: sv_instancebaselines
Locked ConVar: sv_useexplicitdelete
Locked ConVar: cl_interpolate
Locked ConVar: dbg_demofile
Locked ConVar: r_entity
Locked ConVar: sv_stressbots
Locked ConVar: sv_sendtables
Locked ConVar: sv_creationtickcheck
Some of them can be funny:
tf_scout_stunball_ball_regen_rate but if 0 a server becomes laggy
sv_proj_stunball_damage - the damage by sandman's ball
tf_scout_air_dash_count - the number of scout jumps
with these cvars you can make air battles like in FF
tf_sniper_jar_regen_rate - I think you understood