Function and Signal Switchers, Mixers, Signal Splitters
No A/B stompboxes are mentioned here, cause there are too many out there. Check out products from Roger Mayer, Collins, Boss, Nobels, Peter Frampton, Morley, DOD, Palmer,, etc. and DIY websites.

360 Systems:
AM16B   advanced switching/routing matrix

Advanced Tube Technology
Missing Link    19", 1U, stereo 2 loop tube driven mixer, switchable  

MB76   19", 1U, 7 inputs, 6 outputs, prog, midi, mixer/signal router  *

Quad-FX Loop Expander   19", 4 stereo loops to mix with dry signal, 1U  *

HS2 Head Switcher   small, switches 2 ampheads to same speaker  
GRX4   small, router/switcher, 4 loops, midi, etc.  
CFX4   small, 4 function switchers, midi  
AC8   small, universal amplifier controller, midi  
BS2   Guitar Audio Buffer/Splitter, 1 input, 3 buffered outputs, transf. iso. output, phase reverse  
Custom Shop  

Ultralink Pro MX882   19", 1U, stereo multiple line mixer and/or splitter, vol & pan  

Brandstaetter & Rebholz :
SW1-4 Midi Switcher   small, 4 function switchers, midi  *
SW1-8 Midi Switcher   small, 8 function switchers, midi  *
MS1 Mini Split Mixer   small, stereo in/out/send/return, level for send/return/output  *

Matrix   19", 1U, several (stereo) loops, switchers, speaker outputs, etc.

Pete Cornish:   
Custom Shop 

Custom Audio Electronics:   
2x4 Audio Controller   19", 1U, 8 serial loops, 4 function switchers functions, midi (cc only)
4x4 Audio Controller   19", 1U, looper & function switching, midi (cc only)
RL-8   1/2 19", 1U, 8 function switchers, midi (cc only)
Dual Stereo Mini Mixer   1/2 19", 1U, 6 stereo channels, output vol
Amp Selector   19", 1U, 4 amps to one cabinet, power soak, midi (cc only)
RSB-12   19", 2U, 6 loops....   *
RSB-18   19", 2U, 10 loops....   *
Custom Shop

GCX Guitar Audio Switcher   19", 1U, 8 mono loops, midi (cc only)
System Mix Plus   19", 1U, dual stereo line mixer, vol + pan, cab sim, midi (cc only)
System Mix   1/2 19", 1U, dual stereo line mixer

MIDI Switcher Z-11   1/2 19", 1U, 7 function switchers, midi

Custom Shop

Function-Switcher   1/2 19", 8 function switchers, midi
Audio-Switcher    1/2 19", 8 stereo loops, 2 switchable inputs, midi
Combi-Switcher   same as Function-Switcher + 4 stereo loops
Preamp-Switcher   1/2 19", 5 progr preamp loops, midi
MSW4 Microswitcher   small, 4 function switchers, midi
MSW8 Microswitcher   small, 8 function switchers, midi

MS-8   see Nobels MS-8

4x1   stereo switcher   *  
Great Divide   four channel splitter   *

Jester Enterprise:
Hydra Splitter   signal splitter

GS-8   19", 1U, several loops and function switching, midi  *

Kitty Hawk:
Midi Looper   19", 1U, 6 mono loops, 2 function switches, midi in/thru,
Midi Switcher   19", 1U, 5 function switches, 2 momentary switches, AB signal switching

Custom Shop switchers, buffers, etc.

Lake Butler:
MS1-8   8 function switcher   *

London Power:
Sorcerer   19", 2U, dual effectloop controller, 2 loops, tube driven
Stage Link   19", 2U, switch between 2 amps and one cabinet

SLM-82   19", 1U, 8 input, 2 output, vol & pan per channel
SLE-82    Same as above + fx loop and mix control

Mix Box   small, tube driven 4 channel mixer   *

Midi Matrix   19", 2U, 6 audo loops, 10 function switchers, midi   *
High Gain Amp Switcher    19", 1U, switches 4 between amps    *

MvH Design:
Custom A/B Switcher   small, 1 input, 2 outputs, 1 footswitch, remotely controlled noiseless A/B switcher, DIY  

MS-8    19", 8 function switchers, midi  *  
Alex-1   small, 1 loop
Split-4   small, split 1 signal to 4
Mix-41C   small, 4 mono in, 1 mono out, level controls
Mix-42C   small, 4 mono in, stereo out, level + pan controls
SPX-31   small, parallel loop, 2 send + 2 return, level controls
MS-4   small, 4 function switchers, midi
MV-C   small, midi progr volume control
A/B-V   small, 2 switchable in- & outputs, level

PGA-02   small, switches 2 amp outputs to one speaker
PGA-03   small, active signal splitter

Midi Pro   19", 1U, 4 audio loops, 8 function switchers, midi   *

SM26(B)   19" line mixer/splitter, 1U
MLM 82a   19" mic/line mixer, 1U
SM82   19" line mixer, 1U

Midi Octopus   1/2 19", 8 function switchers, midi  *  
Dual Remote Loop  *
G612 Linemixer  *

Patchmate   19", 9 stereo loops or function switchers, hush, midi   *  
Rack Interface   19", mono/stereo patchbay, ext. wah + vol, mixer, speaker sim, etc.  *
RSB-12   19", 2U, 6 loops....  *
RSB-18   19", 2U, 10 loops....  *

RP93S Patchworks   19", 1U, 4 stereo audio loops, 4 function switchers, midi

Sound Sculpture:   
Switchblade GL   19", 1U, ultra advanced audio routing matrix, 16 balanced in/out, 8 function switches, full midi
Switchblade 16    as above?   *?
Switchblade Studio   as above but for higher in/output signals
Switchblade 8B   as above but with 8 in/out
Switchblade 8   as 8B but unbalanced
MC-8 Crosspatch   advanced switching matrix, 19", 1U, 8 in/out, midi    *
MidiUp   small, volumepot/pedal convertor to (various) midi
ABCadabra   small, signal router 2in/out, midi
Footsim   small, 7 function switching, midi

TC Electronic:   
2290 Delay    5 audio loops, 4 mono, 1 stereo  *

Mac 1     19", 2u, 8 serial and 2 par. loops, VCA, midi

Uptown Technology:
Flash   audio routing matrix   *

Valve Effect Loop Buffer   19", 1U, 2 mono loops, tube buffered   *