LAS-LAX is probably my most favorite route. I fly it about 5 times a week yet never get bored of it. I usually fly 757s or 737s and sometimes I take a JAL 744 or Hawaiian DC10. JAL did operate the 744 LAS-LAX but you could not book LAS-LAX, it was only to pick up passengers at LAX to continue to NRT. Hawaiian also does operate a DC10 LAS-LAX. It's a pretty short, fun little route.
SEA to HLN - Horizon CRJ700
CVG to PVD - Delta 737-800 or MD-83
BOS to MDW - Metrojet 737-200
ORD to LAX - American MD-82
ORD to MIA - American MD-82
ORD to BOS - American MD-82
ORD to SLC - American MD-82
SLC to HLN - SkyWest CRJ500
SLC to PHX - SkyWest CRJ500
SEA to ANC - Alaska 737-400
IAH to DEN - Continental 737
ORD to DCA - American MD-82
CGX to CMI or IKK - Piper Navajo
The Learjet 45 from anywhere to anywhere.
SLC to BTM - Skywest CRJ
And the list continues...
I also really like to practice holding, approaches, and partial panel stuff with the Cessna 182 and 182RG.
I did LHR-SEA today till the game froze while going over Boeing Field on a 4 mile final!
LHR 09 Departure
EPH(yea i didnt bother with NATs!)
then the EPH arrival procedure.