For Those watching the watch keynote closely, there were 64 icons on the Apple watch at Demo timecode [01:17:00]
Feel free to copy this list and update it as new information comes available:
All of these are seen on the device.
E03) Clock - The main clock with configurable faces.
B09) Timer - Countdown timer
A09) Stopwatch - Designed for common and sports scenarios.
E02) World Clock
E05) Fitness - Move, Stand and Exercise "Rings" on the screen game-ify basic fitness with achievements (badges)
E04) Workout -monitoring for running, cycling etc.
???) Siri - Various integration points, including rotten tomatoes (movies).
D03) Music - No details on storage.
C04) Weather - No details.
C05) Calendar - Supports "Glances" for next meeting etc.
D09) iTunes Remote - Blue play icon. remote play iphone or airplay music.
E09) Photos - Favourited collections and photos only, show in mosaic and allow zooming.
A06) Passbook - Support for Apple Pay. Default card will show when next to NFC, contact with skin (and passcode entry, when the watch is put on) is required.
D02) Maps - Walking directions with vibrating "go left/right" feedback.
D10) Settings - Obvious requirement.
C09) Messages - Quick replies and notifications imessage and SMS.
C08) Phone Dialer - No details
E11) Camera Remote - Shows video feed. Great for gigs if you're short. Good for iPhone camera timer.
B10) Stocks - Much like apple’s iOS app.
E01) Alarm Clock - Yet another separate clock app.
E07) Mail - Basic email functionality, including smart replies (reads emails for common responses)
D08) Calculator - Basic calc, probably not scientific due to screen size.
E12) Heart Monitor - Red icon with white heart, with heartbeat going through it.
--- Possible ---
B12) Workout - Old Workout app icon or raw workout data
C11) Fitness - Old Fitness app icon or raw fitness data. Same icon as in Health iOS8 app.
B03) Sleep Monitor - possible sleep monitoring and suggestions
Announced Vendor Applications
Not all of these were seen on the home screen.
A13) BMW i Connected Drive
B06) American Airlines
B07) HoneyWell Lyric - thermostat control
C02) Starwood Hotels
C07) Lutron - lighting control
C10) Major League Baseball
E10) City Mapper - public transport route finder
---Discovered, not announced---
A10) Whole Pantry - Healthy recipes
A11) Telegram - Messenger app
B11) QQ - messenger, calling app.
C06) AT&T Voicemail Viewer - visual voicemail
E06) Weibo - Chinese microblog (like twitter/fb)
Icons on the home screen i couldn't identify.
A01) White - Black ‘B’
A02) Blue - white tick
A03) White - Card Game - 4 suits
A04) Red - with orange "Cc" text logo
A08) Orange - with white Mail envelope
A12) Grey -with 5 multi-colored ‘splashes’ out from the center.
A13) Grey - leaning grey icon with blue “i” in it
B01) Green - with black “3” and “4” flip clock cards.
B02) Green - with a white Explosion and a “B”
B04) Red - with a brown bear/dog
B05) White - 2 arrows red and green pointing at each other.
B08) Green - Lightbulb icon
B13) White - with ABC in colorful writing.
C01) Yellow - with white # symbol
C03) Green - Currency Converter Icon (pound, euro, dollar sign)
C12) Yellow - light yellow with orange Fox
C13) Blue - light blue with a Red heart-shaped plane facing S.
D01) Purple - with basketball net
D04) Green -with a white Percent sign
D05) Grey - with a color painting palette of 7 colors
D11) Light Yellow - bar chart (Numbers?)
D12) Yellow - with a Ladybird
D13) Green - 4 people sat at a table?
E08) Grey - with a purple ‘carriage return’ character
thanks to: jiashuw, rcastro0, x13gamer, talonfast, jayleb, mknapper1