In reply to a lakeland climber: Agree with leaving your bike before Luibeg. Tend to leave mine about half a mile earlier than the edge of the plantation at the end of the new improved path which finishes as you come out of the trees at 0268 9394. Once met a couple on mountain bikes after Luibeg - they were doing a loop round Sgor Mor - although looking fit and competent they were finding it a real struggle.
As for Munros made easier by bike - well most of the Cairngorms for starters:
Mount Keen from Glen Tanar or even Glen Esk though it's a short day anyway, hills accessed from Glen Callater, from Glen Taitneach at Spittal of Glen Shee, Lochnagar, Broad Cairn and hills from Glas Allt Shiel, Beinn a' Bhuird, Ben Avon from various start points, not just Keiloch, Bynack Mor from the road end after Glen More Lodge, Meall Chuaich, Beinn Dearg from Calvine. Enough, enough I hear you cry! OK one more that I've not biked myself is Mullach Clach a Bhlair from Glen Feshie; I've seen guys cycle right up and do a loop that included Carn Ban Mor but it looked a right grind going up and the track down from Carn Ban Mor looks a bit difficult on a bike.
One non Cairngorm suggestion and then I'm stopping: from the concrete bridge at the W end of Loch laggan you can get access to loads of hills including a rarely used way up Beinn na Lap.