I thought I would start a thread on unusual items & part numbers for the Hexheads only, as a companion to the list at the top of the Oilheads Forum.
Everyone, if you have any additions, corrections, please feel free to add on.
I believe the list to be accurate, but my only warranty of it is a refund of what you paid for it.) 
In no particular order:
Oil Filter BMW - 11 42 7 673 541
Walmart - ST3614 *
Bosch - 3330 *
Advance AutoParts AA3614 *
* Any of the Oilhead filters will work, but they are longer
Crush Washers16 x 20 x 1.5 mm (engine drain) - 07 11 9 963 252
14 x 18 x 1.5 mm (final drive drain) - 07 11 9 963 200
18 x 22 x 1.5 mm (transmission fill and drain)- 07 11 9 963 300
Hexhead Maintainance Schedule Click Here to go to the Schedules3 Pin Connector Repair Kit - 83 30 0 402 341
(As used on the on-plug ignition coils)
Clutch Circuit Mineral Oil -
07 51 0 398 495 21 52 0 392 546
Alternative - Magura Service Kit - MAG107 Source -
Magura Kit Updated Left Side Cam Chain Tensioner Piston/CylinderPiston - 11 31 7 656 922
Cylinder - 11 31 7 688 629
Spark PlugsNGK DCPR8EKC
Bosch YR5LDE
Denso DCPR7EIX (IXU22) single electrode Iridium
Denso DCPR8EIX (IXU24) single electrode Iridium
Denso DCPR8EKC double electrode
Battery -
R1200GS - Odyssey PC535 or Yuasa YTX14-BS
(GS, not sure about for others)R1200RT - Odyssey PC680 (with slight modifications) or from ebatteriestogo.com - Universal Battery, part number UB22-12N
Updated EWS Pickup Ring -
61 35 7 714 207 61 35 7 705 247 (as of 06/08)
Aftermarket Alternator Belt
NAPA part # 040233, 9/16" x 24-3/8" 14mm x 620mm. The BMW PN translates to a 4PK592Oetiker Intake Type 168 Clamp Tool - 14002121-TLQ
From EFC International, St. Louis, MO
Silver Frame / Wheel Paint DupliColor - DSGM340 Silver
DupliColor - DS125 Clear Top Coat
Piedmont Red Touchup PaintColor Rite code BMW 8110
BMW Paint Codes ListGo here -
BMW Paint Codes Wiring Diagrams CD - 06 73 7 713 999
Service Manual DVD -
01 79 7 706 308 01 59 7 720 810
Accessory Front Power Take Off Connector (e.g for a GPS) - 83 30 0 413 585
R1200RT Accessory Rear Power Take Off Connector for direct battery power - 61 12 7 701 299
Round Clutch & Brake Reservoir Cap Removal Tool - 90 88 6 321 511
Quality Metal On-plug Coil Removal Tool - 90 88 6 123 561
Flywheel/Engine Locking Tool - 90 88 6 112 650
90° Fuel Line Quick Disconnect - 13 53 7 674 765
Updated Anti-shudder Brake Rotor Rubberized Stop Disc (Set) 34 11 7 697 384 (13.7 mm)
34 11 7 697 387 (8.5 mm)
R1200GS Adventure Winglets for Standard R1200GS 46 63 7 694 400 Right
46 63 7 694 399 Left
06 32 7 657 966 Screw, qty 4
46 61 2 308 594 Washer, qty 4
46 63 7 664 846 Bushing, qty 4
07 12 9 900 645 Nut, qty 4
R1200RT-P Under Mirror Aux. Light Brackets46 63 7 692 869 (Left)
46 63 7 692 870 (Right)
RT-P switches and housing61 31 7 689 809 Fog light switch
61 31 7 653 974 Housing, front half
61 31 7 660 446 Housing, back half
61 31 7 653 978 Bracket
65 14 7 651 032 Screw, M3x12, qty 2
07 11 9 906 411 Screw, M4x16, qty 2
46 63 2 313 281 Screw, M5x12, qty 1
To add the R1200RT-P engine oil cooler fan to a standard R1200RT46 63 7 690 869 Fan Shroud, qty 1
17 11 7 656 030 Fan, qty 1
07 11 9 931 026 Washer, qty 3
63 12 7 682 829 Bolt, qty 3
06 32 7 651 204 Bolt, qty 2
51 12 7 070 202 Clip Nut, qty 2
To modify the R120RT rear accessory socket for direct battery power without cutting the OEM wires:61 12 7 701 299 Adaptor Lead
Add-on rear mudflap extension for R1200RT71 60 7 694 184 Mudguard
46 61 7 677 527 Flanged cap screw M5x12
07 11 9 903 070 Hex nut M5-A2-70
To Convert a later model single-horn R1200RT to US model year 2005 dual-horns61 33 8 381 271 Horn
61 33 7 655 882 Horn
46 71 7 675 209 Screw
61 33 1 459 545 Cage Nut
R1200RT (05-09)tire sizesFront 120/70ZR17
Rear 180/55ZR17
To add R1200S mirrors to an R1200RT51 16 7 653 773 Left mirror
51 16 7 653 774 Right mirror
51 16 2 328 287 Nut, qty 2
51 16 2 309 607 Washer, qty 2
To add R1200GS mirrors to an R1200RT51 16 2 307 769 Mirror, qty 2
51 16 2 309 607 Washer, qty 2
51 16 2 328 287 Nut, qty 2