Valentines Combee is a 2012 event Pokemon released on Feb. 5 which could be found if you bought honey and brought it to a location at which you can slather honey.
Everstone%: 1 in 50 (2%)
Usable for Bright/ShiningPowder Breeding?: No
Encounter Method (Map): Use Honey in applicable areas in Sinnoh (example: Floaroma Meadow). Combee has a 20% chance of appearing when you use Honey. 1 out of 5 times, it'll be a Valentine's Combee. Thus, the encounter ratio is 4%, or 1 in 25.
Alternate Method (Held Item): Give a Chocolate Heart for a Combee (HGSS sprite only; won't work onspecial natures) to hold and it'll turn into Valentine's Combee. This won't work on Vespiquen - it must be used on Combee.
Shiny% (map): Normal chance.Shiny% (held item): 1 in 10 (10%). 100% if shiny when given the item.
Note: Valentine's Vespiquen can only be obtained by evolving a female Valentine's Combee.
Chocolate Hearts were available in 2011's Valentine's Day event. In 2012 users were able to send "v-mail" to each other while attaching these Chocolate Hearts, so that new users could use the Chocolate Hearts.