Place, height, mode of transport. Hopefully this'll throw up a few interesting stories. I'll start: -

Personal highest (PH) - Top of the top top glacier, Les Deux Alpes, France, about 3550m, snowboard

On foot - Tracuit Cabin, Anniviers Valley, nr Zinal, Switzerland, 3256m

Bike - Cime de la Bonette, France, 2802m

The bike one was definitely the hardest, snowboard the most memorable - perfect clear day, you could see virtually everything, Mont Blanc looked amazing! Tracuit Cabin, great soup!